Difference between revisions of "Nature" - New World Encyclopedia
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− | {{ | + | {{About|the physical universe}} |
+ | {{Redirect2|Natural|Natural World}} | ||
+ | <!-- [[Natural World]] redirects here, make it easier to find [[Natural World (BBC TV Series)]] —> | ||
+ | {{See also|Natural environment}} | ||
− | [[ | + | [[File:Hopetoun falls.jpg|thumb|310px|<center>[[Hopetoun Falls]], [[Australia]]</center>]] |
− | [[ | + | [[File:Bachalpseeflowers.jpg|thumb|310px|<center>[[Bachalpsee]] in the [[Swiss Alps]]</center>]] |
− | + | [[File:Galunggung.jpg|thumb|right|310px|[[Lightning]] strikes during the eruption of the huge [[Galunggung]] [[volcano]], [[West Java]], in 1982]] | |
− | + | '''Nature''', in the broadest sense, is equivalent to the '''natural world''', '''physical world''', or '''material world'''. "Nature" refers to the [[phenomenon|phenomena]] of the physical world, and also to [[life]] in general. It ranges in scale from the [[subatomic]] to the [[universe|cosmic]]. | |
− | + | The word ''nature'' is derived from the Latin word ''natura'', or "essential qualities, innate disposition", and in ancient times, literally meant "birth".<ref name="etymonline-nature">{{OEtymD|nature|accessdate=2006-09-23}}</ref> ''Natura'' was a Latin translation of the Greek word ''[[physis]]'' (φύσις), which originally related to the intrinsic characteristics that plants, animals, and other features of the world develop of their own accord.<ref>A useful though somewhat erratically presented account of the pre-Socratic use of the concept of φύσις may be found in Naddaf, Gerard ''The Greek Concept of Nature'', SUNY Press, 2006. The word φύσις, while first used in connection with a plant in Homer, occurs very early in Greek philosophy, and in several senses. Generally, these senses match rather well the current senses in which the English word ''nature'' is used, as confirmed by Guthrie, W.K.C. ''Presocratic Tradition from Parmenides to Democritus'' (volume 2 of his ''History of Greek Philosophy''), Cambridge UP, 1965.</ref><ref>The first known use of ''physis'' was by [[Homer]] in reference to the intrinsic qualities of a plant: ὣς ἄρα φωνήσας πόρε φάρμακον ἀργεϊφόντης ἐκ γαίης ἐρύσας, καί μοι '''φύσιν''' αὐτοῦ ἔδειξε. (So saying, Argeiphontes [=Hermes] gave me the herb, drawing it from the ground, and showed me its '''nature'''.) ''[[Odyssey]]'' 10.302-3 (ed. A.T. Murray). (The word is dealt with thoroughly in Liddell and Scott's ''[http://archimedes.fas.harvard.edu/pollux Greek Lexicon]''.) For later but still very early Greek uses of the term, see earlier note.</ref> The concept of nature as a whole, the physical [[universe]], is one of several expansions of the original notion; it began with certain core applications of the word φύσις by [[Pre-Socratic philosophy|pre-Socratic]] philosophers, and has steadily gained currency ever since. This usage was confirmed during the advent of modern [[scientific method]] in the last several centuries.<ref>Isaac Newton's [[Philosophiae Naturalis Principia Mathematica]] (1687), for example, is translated "Mathematical Principles of Natural Philosophy", and reflects the then-current use of the words "[[natural philosophy]]", akin to "systematic study of nature"</ref><ref>The etymology of the word "physical" shows its use as a synonym for "natural" in about the mid-15th century: {{OEtymD|physical|accessdate=2006-09-20}}</ref> | |
− | + | Within the various uses of the word today, "nature" may refer to the general realm of various types of living plants and animals, and in some cases to the processes associated with inanimate objects–the way that particular types of things exist and change of their own accord, such as the [[weather]] and [[geology]] of the Earth, and the [[matter]] and [[energy]] of which all these things are composed. It is often taken to mean the "[[natural environment]]" or [[wilderness]]–wild animals, rocks, forest, beaches, and in general those things that have not been substantially altered by human intervention, or which persist despite human intervention. For, example, manufactured objects and human interaction generally are not considered part of nature, unless qualified as, for example, "human nature" or "the whole of nature". This more traditional concept of natural things which can still be found today implies a distinction between the natural and the artificial, with the artificial being understood as that which has been brought into being by a human [[consciousness]] or a human [[mind]]. Depending on the particular context, the term "natural" might also be distinguished from the [[Wikt:unnatural|unnatural]], the [[supernatural]], and the [[Artifact (archaeology)|artifactual]]. | |
− | [[ | ||
− | |||
− | + | ==Earth== | |
+ | [[File:The Earth seen from Apollo 17.jpg|thumb|right|200px|upright|right|View of the [[Earth]], taken in 1972 by the [[Apollo 17]] [[astronaut]] crew. This image is the only photograph of its kind to date, showing a fully sunlit hemisphere of the Earth.]] | ||
+ | {{Main|Earth|Earth science|Structure of the Earth|Plate tectonics|Geology}} | ||
− | + | [[Earth]] (or, "the earth") is the only [[planet]] presently known to support life, and its natural features are the subject of many fields of scientific research. Within the [[solar system]], it is third nearest to the sun; it is the largest [[terrestrial planet]] and the fifth largest overall. Its most prominent climatic features are its two large polar regions, two relatively narrow [[temperate]] zones, and a wide [[equator]]ial [[tropical]] to [[subtropical]] region.<ref> | |
+ | {{cite web | ||
+ | | url=http://www.blueplanetbiomes.org/climate.htm | ||
+ | | title=World Climates | ||
+ | | work=Blue Planet Biomes | ||
+ | | accessdate=2006-09-21 | ||
+ | }}</ref> [[precipitation (meteorology)|Precipitation]] varies widely with location, from several [[metre]]s of water per year to less than a [[millimetre]]. 71 percent of the Earth's surface is covered by salt-water oceans. The remainder consists of continents and islands, with most of the inhabited land in the [[Northern Hemisphere]]. | ||
− | Earth has evolved through geological and biological processes that have left traces of the original conditions. The [[Crust (geology)|outer surface]] is divided into several [[tectonic plate]]s | + | Earth has evolved through geological and biological processes that have left traces of the original conditions. The [[Crust (geology)|outer surface]] is divided into several gradually migrating [[tectonic plate]]s, which have changed relatively quickly several times. {{Citation needed|date=April 2010}} The interior remains active, with a thick layer of molten [[Earth mantle|mantle]] and an iron-filled core that generates a [[magnetic field]]. |
− | The [[atmosphere|atmospheric]] conditions have been significantly altered from the original conditions by the presence of life forms,<ref> | + | The [[atmosphere|atmospheric]] conditions have been significantly altered from the original conditions by the presence of life-forms,<ref>{{cite web | date = 2005-09-11 | url = http://www.sciencedaily.com/releases/2005/09/050911103921.htm | title = Calculations favor reducing atmosphere for early Earth | publisher = Science Daily | accessdate = 2007-01-06 }}</ref> which create an ecological balance that stabilizes the surface conditions. Despite the wide regional variations in climate by [[latitude]] and other geographic factors, the long-term average global climate is quite stable during interglacial periods,<ref>{{cite web | url = http://www.epa.gov/climatechange/science/pastcc.html | title = Past Climate Change | publisher = U.S. Environmental Protection Agency | accessdate = 2007-01-07 }}</ref> and variations of a degree or two of average global temperature have historically had major effects on the ecological balance, and on the actual geography of the Earth.<ref>{{cite web | author=Hugh Anderson, Bernard Walter | date = March 28, 1997 | url = http://vathena.arc.nasa.gov/curric/land/global/climchng.html | title = History of Climate Change | publisher = NASA | accessdate = 2007-01-07 |archiveurl = http://web.archive.org/web/20080123130745/http://vathena.arc.nasa.gov/curric/land/global/climchng.html |archivedate = 2008-01-23}}</ref><ref>{{cite web | last = Weart | first = Spencer | month = June | year = 2006 | url = http://www.aip.org/history/climate/ | title = The Discovery of Global Warming | publisher = American Institute of Physics | accessdate = 2007-01-07 }}</ref> |
+ | |||
+ | ===Geology=== | ||
+ | {{Main|Geology}} | ||
+ | [[Image:Tectonic plate boundaries.png|thumb|right|300px|Three types of geological [[plate tectonic]] boundaries.]] | ||
+ | Geology is the [[science]] and study of the solid and liquid matter that constitutes the [[Earth]]. The field of geology encompasses the study of the composition, [[structural geology|structure]], [[Physical property|physical properties]], dynamics, and [[History of the Earth|history]] of [[Earth materials]], and the processes by which they are formed, moved, and changed. The field is a major [[academic discipline]], and is also important for [[mining|mineral]] and [[petroleum geology|hydrocarbon]] extraction, knowledge about and mitigation of [[natural hazard]]s, some [[Geological and geophysical engineering|engineering]] fields, and understanding [[Paleoclimatology|past climates]] and environments. | ||
+ | |||
+ | ====Geological evolution==== | ||
+ | The geology of an area evolves through time as rock units are deposited and inserted and deformational processes change their shapes and locations. | ||
+ | |||
+ | Rock units are first emplaced either by [[deposition (geology)|deposition]] onto the surface or intrude into the [[Country rock (geology)|overlying rock]]. Deposition can occur when [[sediment]]s settle onto the surface of the Earth and later [[lithification|lithify]] into [[sedimentary rock]], or when as [[volcanic rock|volcanic material]] such as [[volcanic ash]] or [[lava flow]]s, blanket the surface. [[Igneous intrusion]]s such as [[batholith]]s, [[laccolith]]s, [[dike (geology)|dike]]s, and [[sill (geology)|sills]], push upwards into the overlying rock, and crystallize as they intrude. | ||
+ | |||
+ | After the initial sequence of rocks has been deposited, the rock units can be [[deformation (mechanics)|deformed]] and/or [[metamorphism|metamorphosed]]. Deformation typically occurs as a result of horizontal shortening, [[extension (geology)|horizontal extension]], or side-to-side ([[strike-slip]]) motion. These structural regimes broadly relate to [[convergent boundary|convergent boundaries]], [[divergent boundary|divergent boundaries]], and [[transform boundary|transform boundaries]], respectively, between [[plate tectonics|tectonic plates]]. | ||
===Historical perspective=== | ===Historical perspective=== | ||
− | {{ | + | {{Main|History of Earth|Evolution}} |
− | [[Image: | + | [[Image:Pangea animation 03.gif|thumb|left|325px|An animation of the [[Earth]]'s hypothesized [[Pangaea]] separation.]] |
− | + | [[Image:Hyperia.jpg|thumb|left|200px|[[Plankton]] inhabit oceans, seas and lakes, and have existed on the [[Earth]] for at least 2 billion years.<ref>{{cite book|last=Margulis|first=Lynn|coauthors=Dorian Sagan |year=1995|title=What is Life?|publisher=Simon & Schuster|location=New York|isbn=0684813262}}</ref>]] | |
+ | <!-- Images End —> | ||
+ | Earth is estimated to have formed 4.54 billion years ago from the [[solar nebula]], along with the [[Sun]] and other [[planet]]s.<ref>{{cite book |first=G. Brent |last=Dalrymple |year=1991 |title=The Age of the Earth |publisher=Stanford University Press |location=Stanford |isbn=0-8047-1569-6}}</ref> The moon formed roughly 20 million years later. Initially molten, the outer layer of the planet cooled, resulting in the solid crust. Outgassing and [[Volcano|volcanic]] activity produced the primordial atmosphere. Condensing [[water vapor]], most or all of which came from [[ice]] delivered by [[comet]]s, [[Origin of the world's oceans|produced the oceans]] and other water sources.<ref> | ||
+ | {{cite journal | ||
+ | | first=A. | ||
+ | | last=Morbidelli | ||
+ | | coauthors=''et al.'' | ||
+ | | year=2000 | ||
+ | | url=http://adsabs.harvard.edu/abs/2000M&PS...35.1309M | ||
+ | | title=Source Regions and Time Scales for the Delivery of Water to Earth | ||
+ | | journal=Meteoritics & Planetary Science | ||
+ | | volume=35 | ||
+ | | issue=6 | ||
+ | | pages=1309–1320 | ||
+ | | doi=10.1111/j.1945-5100.2000.tb01518.x | ||
+ | }}</ref> The highly energetic chemistry is believed to have produced a self-replicating molecule around 4 billion years ago.<ref> | ||
+ | {{cite news | ||
+ | | title=Earth's Oldest Mineral Grains Suggest an Early Start for Life | ||
+ | | publisher=NASA Astrobilogy Institute | ||
+ | | date=2001-12-24 | ||
+ | | url=http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=76 | ||
+ | | accessdate=2006-05-24 | ||
+ | }}</ref> | ||
+ | |||
+ | Continents formed, then broke up and reformed as the surface of Earth reshaped over hundreds of millions of years, occasionally combining to make a [[supercontinent]]. Roughly 750 million years ago, the earliest known supercontinent [[Rodinia]], began to break apart. The continents later recombined to form [[Pannotia]] which broke apart about 540 million years ago, then finally [[Pangaea]], which broke apart about 180 million years ago.<ref>{{cite journal |first=J.B. |last=Murphy |coauthors=R.D. Nance |year=2004 |url=http://www.americanscientist.org/issues/page2/how-do-supercontinents-assemble |title=How do supercontinents assemble? |journal=American Scientist |volume=92 |issue=4 |doi=10.1511/2004.4.324 | pages = 324}}</ref> | ||
− | + | There is significant evidence that a severe [[Glacier|glacial]] action during the [[Neoproterozoic]] era covered much of the planet in a sheet of ice. This hypothesis has been termed the "[[Snowball Earth]]", and it is of particular interest as it precedes the [[Cambrian explosion]] in which multicellular life forms began to proliferate about 530–540 million years ago.<ref>{{cite book |first=J.L. |last=Kirschvink |year=1992 |chapter=Late Proterozoic Low-Latitude Global Glaciation: The Snowball Earth |chapterurl=http://www.gps.caltech.edu/~jkirschvink/pdfs/firstsnowball.pdf |title=The Proterozoic Biosphere |editor=J.W. Schopf, C. Klein eds. |publisher=Cambridge University Press |location=Cambridge |pages=51–52 |isbn=0-521-36615-1}}</ref> | |
− | + | Since the [[Cambrian explosion]] there have been five distinctly identifiable [[Extinction event|mass extinctions]].<ref>{{cite journal |last=Raup |first=David M. |coauthors=J. John Sepkoski Jr. |year=1982 |month=March |title=Mass extinctions in the marine fossil record |journal=Science |volume=215 |issue=4539 | pages = 1501–3 |doi=10.1126/science.215.4539.1501 |pmid=17788674}}</ref> The last mass extinction occurred some 65 million years ago, when a meteorite collision probably triggered the extinction of the [[Bird|non-avian]] [[dinosaur]]s and other large reptiles, but spared small animals such as [[mammal]]s, which then resembled [[shrew]]s. Over the past 65 million years, mammalian life diversified.<ref>{{cite book |last=Margulis |first=Lynn |coauthors=Dorian Sagan |year=1995 |title=What is Life? |publisher=Simon & Schuster |location=New York |isbn=0-684-81326-2 |pages=145}}</ref> | |
− | [[ | + | Several million years ago, a species of small African [[ape]] gained the ability to stand upright.<ref>{{cite book |last=Margulis |first=Lynn |coauthors=Dorian Sagan |year=1995 |title=What is Life? |publisher=Simon & Schuster |location=New York |isbn=0-684-81326-2}}</ref> The subsequent advent of human life, and the development of agriculture and further [[civilization]] allowed humans to affect the Earth more rapidly than any previous life form, affecting both the nature and quantity of other organisms as well as global climate. By comparison, the [[oxygen catastrophe]], produced by the proliferation of [[algae]] during the [[Siderian]] period, required about 300 million years to culminate. |
− | |||
− | + | The present era is classified as part of a [[mass extinction]] event, the [[Holocene extinction event]], the fastest ever to have occurred.<ref>{{cite journal | author = Diamond J | title = The present, past and future of human-caused extinctions | journal = Philos Trans R Soc Lond B Biol Sci | volume = 325 | issue = 1228 | pages = 469–76; discussion 476–7 | year = 1989 | pmid = 2574887 | doi = 10.1098/rstb.1989.0100 | last2 = Ashmole | first2 = N. P. | last3 = Purves | first3 = P. E.}}</ref><ref>{{cite journal | author = Novacek M, Cleland E | title = The current biodiversity extinction event: scenarios for mitigation and recovery | journal = Proc Natl Acad Sci USA | volume = 98 | issue = 10 | pages = 1029 | year = 2001 | pmid = 11344295 | doi = 10.1073/pnas.091093698 | pmc = 33235}}</ref> Some, such as [[E. O. Wilson]] of [[Harvard University]], predict that human destruction of the [[biosphere]] could cause the extinction of one-half of all species in the next 100 years.<ref>"The mid-Holocene extinction of silver fir ''(Abies alba)'' in the ..." [http://www.springerlink.com/index/D85T53513002564V.pdf pdf]</ref> The extent of the current extinction event is still being researched, debated and calculated by biologists.<ref>See, e.g. [http://park.org/Canada/Museum/extinction/holmass.html], [http://park.org/Canada/Museum/extinction/extincmenu.html], [http://park.org/Canada/Museum/extinction/patterns.html]</ref> | |
+ | {{br}} | ||
− | + | ==Atmosphere, climate, and weather== | |
+ | [[Image:Top of Atmosphere.jpg|thumb|300px|[[Rayleigh scattering|Blue light is scattered more]] than other wavelengths by the gases in the [[atmosphere]], giving the Earth a blue [[Halo (optical phenomenon)|halo]] when seen from space]] | ||
+ | {{Main|Earth's atmosphere|Climate|Weather}} | ||
− | The | + | The atmosphere of the Earth serves as a key factor in sustaining the planetary [[Nature#Ecosystems|ecosystem]]. The thin layer of [[gas]]es that envelops the Earth is held in place by the planet's gravity. Dry [[air]] consists of 78% [[nitrogen]], 21% [[oxygen]], 1% [[argon]] and other [[inert gases]], carbon dioxide, etc.; but air also contains a variable amount of [[water vapor]]. The atmospheric pressure declines steadily with altitude, and has a [[scale height]] of about 8 [[kilometre]]s at the Earth's surface: the height at which the atmospheric pressure has declined by a factor of ''[[E (mathematical constant)|e]]'' (a mathematical constant |
+ | equal to 2.71...).<ref>{{cite web | ||
+ | | url = http://www.grc.nasa.gov/WWW/K-12/Numbers/Math/Mathematical_Thinking/ideal_gases_under_constant.htm | title = Ideal Gases under Constant Volume, Constant Pressure, Constant Temperature, & Adiabatic Conditions | publisher = NASA | accessdate = 2007-01-07 | ||
+ | }}</ref><ref>{{cite journal | last = Pelletier | first = Jon D. | title=Natural variability of atmospheric temperatures and geomagnetic intensity over a wide range of time scales | journal=Proceedings of the National Academy of Sciences | year=2002 | volume=99 | pages=2546–2553 | doi= 10.1073/pnas.022582599 | pmid=11875208 | pmc = 128574 }}</ref> The [[ozone layer]] of the Earth's atmosphere plays an important role in depleting the amount of [[ultraviolet]] (UV) radiation that reaches the surface. As [[DNA]] is readily damaged by UV light, this serves to protect life at the surface. The atmosphere also retains heat during the night, thereby reducing the daily temperature extremes. | ||
− | + | Terrestrial weather occurs almost exclusively in the [[troposphere|lower part of the atmosphere]], and serves as a convective system for redistributing heat. [[Ocean current]]s are another important factor in determining climate, particularly the major underwater [[thermohaline circulation]] which distributes heat energy from the equatorial oceans to the polar regions. These currents help to moderate the differences in [[temperature]] between winter and summer in the temperate zones. Also, without the redistributions of heat energy by the ocean currents and atmosphere, the tropics would be much hotter, and the [[polar region]]s much colder. | |
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− | + | Weather can have both beneficial and harmful effects. Extremes in weather, such as [[tornado]]es or [[hurricane]]s and [[cyclone]]s, can expend large amounts of energy along their paths, and produce devastation. Surface vegetation has evolved a dependence on the seasonal variation of the weather, and sudden changes lasting only a few years can have a dramatic effect, both on the vegetation and on the animals which depend on its growth for their food. | |
− | |||
− | + | [[File:Dszpics1.jpg|thumb|right|280px|<center>A tornado in central [[Oklahoma]].</center>]] | |
The planetary climate is a measure of the long-term trends in the weather. Various factors are known to [[Climate change|influence the climate]], including ocean currents, surface [[albedo]], [[greenhouse gas]]es, variations in the solar luminosity, and changes to the planet's orbit. Based on historical records, the Earth is known to have undergone drastic climate changes in the past, including [[ice age]]s. | The planetary climate is a measure of the long-term trends in the weather. Various factors are known to [[Climate change|influence the climate]], including ocean currents, surface [[albedo]], [[greenhouse gas]]es, variations in the solar luminosity, and changes to the planet's orbit. Based on historical records, the Earth is known to have undergone drastic climate changes in the past, including [[ice age]]s. | ||
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The climate of a region depends on a number of factors, especially [[latitude]]. A latitudinal band of the surface with similar climatic attributes forms a climate region. There are a number of such regions, ranging from the [[tropical climate]] at the equator to the [[polar climate]] in the northern and southern extremes. Weather is also influenced by the [[seasons]], which result from the [[Earth]]'s [[axis of rotation|axis]] being [[axial tilt|tilted]] relative to its [[orbital plane (astronomy)|orbital plane]]. Thus, at any given time during the summer or winter, one part of the planet is more directly exposed to the rays of the [[sun]]. This exposure alternates as the Earth revolves in its orbit. At any given time, regardless of season, the [[northern hemisphere|northern]] and [[southern hemisphere|southern]] hemispheres experience opposite seasons. | The climate of a region depends on a number of factors, especially [[latitude]]. A latitudinal band of the surface with similar climatic attributes forms a climate region. There are a number of such regions, ranging from the [[tropical climate]] at the equator to the [[polar climate]] in the northern and southern extremes. Weather is also influenced by the [[seasons]], which result from the [[Earth]]'s [[axis of rotation|axis]] being [[axial tilt|tilted]] relative to its [[orbital plane (astronomy)|orbital plane]]. Thus, at any given time during the summer or winter, one part of the planet is more directly exposed to the rays of the [[sun]]. This exposure alternates as the Earth revolves in its orbit. At any given time, regardless of season, the [[northern hemisphere|northern]] and [[southern hemisphere|southern]] hemispheres experience opposite seasons. | ||
− | Weather is a [[Chaos theory|chaotic system]] that is readily modified by small changes to the [[Natural environment|environment]], so accurate [[Meteorology|weather forecasting]] is currently limited to only a few days. Overall, two things are currently happening worldwide: (1) temperature is increasing on the average; and (2) regional climates have been undergoing noticeable changes.<ref> | + | Weather is a [[Chaos theory|chaotic system]] that is readily modified by small changes to the [[Natural environment|environment]], so accurate [[Meteorology|weather forecasting]] is currently limited to only a few days.{{Citation needed|date=April 2010}} Overall, two things are currently happening worldwide: (1) temperature is increasing on the average; and (2) regional climates have been undergoing noticeable changes.<ref>{{cite news | title=Tropical Ocean Warming Drives Recent Northern Hemisphere Climate Change | publisher=Science Daily|date=April 6, 2001 | url=http://www.sciencedaily.com/releases/2001/04/010406073554.htm | accessdate=2006-05-24 }}</ref> |
+ | |||
+ | ==Water on Earth== | ||
+ | [[Image:44 - Iguazu - Décembre 2007.jpg|thumb|right|425px|<center>The [[Iguazu Falls|Iguazu waterfalls]] in the border between [[Brazil]] and [[Argentina]].</center>]] | ||
+ | {{Main|Water}} | ||
+ | '''Water''' is a [[chemical substance]] that is composed of [[hydrogen]] and [[oxygen]] and is vital for all known forms of [[life]].<ref>[http://www.un.org/waterforlifedecade/background.html United Nations]</ref> In typical usage, ''water'' refers only to its [[liquid]] form or [[States of matter|state]], but the substance also has a [[solid]] state, [[ice]], and a [[gaseous]] state, [[water vapor]] or [[steam]]. <!--About 1.460 [[Tonne#Multiples|petatonnes]] (Pt) (10<sup>21</sup> kilograms) of water—>Water covers 71% of the [[Earth]]'s surface.<ref>{{cite web|url=https://www.cia.gov/library/publications/the-world-factbook/geos/xx.html#Geo|title=CIA- The world fact book|publisher=[[Central Intelligence Agency]] |accessdate=2008-12-20}}</ref> On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water below ground in [[aquifer]]s and 0.001% in the [[atmosphere|air]] as [[vapor]], [[cloud]]s (formed of solid and liquid water particles suspended in air), and [[precipitation (meteorology)|precipitation]].<ref>[http://www.agu.org/sci_soc/mockler.html Water Vapor in the Climate System], Special Report, [AGU], December 1995 (linked 4/2007). [http://www.unep.org/dewa/assessments/ecosystems/water/vitalwater/ Vital Water] [[UNEP]].</ref> [[Ocean]]s hold 97% of surface water, [[glacier]]s and polar [[ice cap]]s 2.4%, and other land surface water such as [[river]]s, [[lake]]s and [[pond]]s 0.6%. Additionally, a minute amount of the Earth's water is contained within biological bodies and manufactured products. | ||
− | == | + | ===Oceans=== |
− | + | [[Image:Ocean from Leblon.jpg|thumb|left|250px|A view of the [[Atlantic ocean]] from [[Leblon]], [[Rio de Janeiro]].]] | |
− | + | {{Main|Ocean}} | |
+ | {{Five oceans}} | ||
− | [[Image: | + | An [[ocean]] is a major body of [[Seawater|saline water]], and a principal component of the hydrosphere. Approximately 71% of the Earth's [[surface]] (an area of some 361 million square kilometers) is covered by ocean, a [[World Ocean|continuous body of water]] that is customarily divided into several principal oceans and smaller [[sea]]s. More than half of this area is over 3,000 meters (9,800 ft) deep. Average oceanic [[salinity]] is around 35 [[parts per thousand]] (ppt) (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ppt. Though generally recognized as several 'separate' oceans, these waters comprise one global, interconnected body of salt water often referred to as the [[World Ocean]] or global ocean.<ref>"[http://www.answers.com/Ocean#Encyclopedia Ocean]". ''The Columbia Encyclopedia.'' 2002. New York: Columbia University Press</ref><ref name="UNAoO">"[http://www.oceansatlas.com/unatlas/about/physicalandchemicalproperties/background/seemore1.html Distribution of land and water on the planet]". ''[http://www.oceansatlas.com/ UN Atlas of the Oceans]</ref> This concept of a global ocean as a continuous body of water with relatively free interchange among its parts is of fundamental importance to [[oceanography]].<ref>Spilhaus, Athelstan F. 1942 (Jul.). "Maps of the whole world ocean." ''Geographical Review'' ([[American Geographical Society]]). Vol. 32 (3): pp. 431-5.</ref> |
− | + | ||
+ | The major oceanic divisions are defined in part by the [[continent]]s, various [[archipelago]]s, and other criteria: these divisions are (in descending order of size) the [[Pacific Ocean]], the [[Atlantic Ocean]], the [[Indian Ocean]], the [[Southern Ocean]] and the [[Arctic Ocean]]. Smaller regions of the oceans are called [[sea]]s, [[Headlands and bays|gulfs]], [[bay]]s and other names. There are also [[salt lake]]s, which are smaller bodies of landlocked saltwater that are not interconnected with the World Ocean. Two notable examples of salt lakes are the [[Aral Sea]] and the [[Great Salt Lake]]. | ||
+ | |||
+ | ===Lakes=== | ||
+ | [[Image:Lake mapourika NZ.jpeg|thumb|250px|<center>[[Lake Mapourika]], New Zealand</center>]] | ||
+ | {{Main|Lake}} | ||
+ | |||
+ | A [[lake]] (from Latin ''lacus'') is a [[terrain feature]] (or [[physical feature]]), a body of [[liquid]] on the surface of a world that is localized to the bottom of [[Depression (geology)|basin]] (another type of landform or terrain feature; that is, it is not global) and moves slowly if it moves at all. On Earth, a body of water is considered a lake when it is inland, not part of the [[ocean]], is larger and deeper than a [[pond]], and is fed by a river.<ref>{{cite web | ||
+ | |url=http://www.britannica.com/EBchecked/topic/328083/lake | ||
+ | |author=Brittanica online | ||
+ | |accessdate=2008-06-25 | ||
+ | |title=Lake (physical feature) | ||
+ | |quote=[a Lake is] any relatively large body of slowly moving or standing water that occupies an inland basin of appreciable size. Definitions that precisely distinguish lakes, ponds, swamps, and even rivers and other bodies of nonoceanic water are not well established. It may be said, however, that rivers and streams are relatively fast moving; marshes and swamps contain relatively large quantities of grasses, trees, or shrubs; and ponds are relatively small in comparison to lakes. Geologically defined, lakes are temporary bodies of water.}}</ref><ref>{{cite web | ||
+ | |title=Dictionary.com definition | ||
+ | |accessdate=2008-06-25 | ||
+ | |url=http://dictionary.reference.com/browse/lake | ||
+ | a body of fresh or salt water of considerable size, surrounded by land.}}</ref> The only world other than Earth known to harbor lakes is [[Titan (moon)|Titan]], Saturn's largest moon, which has lakes of [[ethane]], most likely mixed with [[methane]]. It is not known if Titan's lakes are fed by rivers, though Titan's surface is carved by numerous river beds. Natural lakes on Earth are generally found in mountainous areas, [[rift zone]]s, and areas with ongoing or recent [[glacier|glaciation]]. Other lakes are found in [[endorheic basin]]s or along the courses of mature rivers. In some parts of the world, there are many lakes because of chaotic drainage patterns left over from the last [[Ice Age]]. All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them. | ||
+ | |||
+ | ====Ponds==== | ||
+ | [[Image:Mill Pond Sunset.jpg|thumb|right|250px|The Westborough Reservoir (Mill Pond) in [[Westborough, Massachusetts]].]] | ||
+ | {{Main|Pond}} | ||
+ | A '''pond''' is a [[body of water|body]] of [[Water stagnation|standing water]], either natural or man-made, that is usually smaller than a [[lake]]. A wide variety of man-made bodies of water are classified as ponds, including [[water garden]]s designed for aesthetic ornamentation, [[fish pond]]s designed for commercial fish breeding, and [[solar pond]]s designed to store thermal energy. Ponds and lakes are distinguished from streams via [[current (stream)|current]] speed. While currents in streams are easily observed, ponds and lakes possess thermally driven microcurrents and moderate wind driven currents. These features distinguish a pond from many other aquatic terrain features, such as [[stream pool]]s and [[tide pool]]s. | ||
+ | |||
+ | ===Rivers=== | ||
+ | [[File:View from Cairo Tower 31march2007.jpg|thumb|275px|left|The [[Nile River]] in [[Cairo]], [[Egypt]]'s capital city]] | ||
+ | {{Main|River}} | ||
+ | |||
+ | A [[river]] is a natural [[watercourse]],<ref>[http://www.merriam-webster.com/dictionary/river River {definition}] from Merriam-Webster. Accessed February 2010.</ref> usually [[freshwater]], flowing toward an [[ocean]], a [[lake]], a [[sea]] or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including [[stream]], creek, brook, rivulet, and rill; there is no general rule that defines what can be called a river. Many names for small rivers are specific to geographic location; one example is ''Burn'' in Scotland and North-east England. Sometimes a river is said to be larger than a creek,<ref>[http://wordnet.princeton.edu/perl/webwn?s=river&sub=Search+WordNet&o2=&o0=1&o7=&o5=&o1=1&o6=&o4=&o3=&h= River], Wordnet</ref> but this is not always the case, due to vagueness in the language.<ref>[http://geonames.usgs.gov/domestic/faqs.htm USGS - U.S. Geological Survey - faqs], #17 What is the difference between [[mountain]], [[hill]], and [[Summit (topography)|peak]]; [[lake]] and [[pond]]; or river and [[stream|creek]]?</ref> A river is part of the [[hydrological cycle]]. Water within a river is generally collected from [[Precipitation (meteorology)|precipitation]] through [[surface runoff]], [[groundwater]] recharge, [[spring (hydrosphere)|springs]], and the release of stored water in natural ice and snowpacks (i.e., from [[glacier]]s). | ||
+ | |||
+ | [[Image:Hawaii Creek.jpg|thumb|right|250px|<center>A rocky [[stream]] in [[Hawaii]].</center>]] | ||
+ | |||
+ | ===Streams=== | ||
+ | {{Main|Stream}} | ||
− | + | A stream is a flowing body of water with a [[Current (stream)|current]], confined within a [[stream bed|bed]] and [[stream bank]]s. In the [[United States]] a stream is classified as a watercourse less than 60 feet (18 metres) wide. Streams are important as conduits in the [[water cycle]], instruments in [[groundwater recharge]], and they serve as corridors for [[fish]] and [[wildlife]] migration. The biological [[habitat]] in the immediate vicinity of a stream is called a [[riparian zone]]. Given the status of the ongoing [[Holocene extinction]], streams play an important [[wildlife corridor|corridor]] role in connecting [[Habitat fragmentation|fragmented habitat]]s and thus in conserving [[biodiversity]]. The study of streams and waterways in general is known as ''surface [[hydrology]]'' and is a core element of [[environmental geography]].<ref>http://ga.water.usgs.gov/edu/hydrology.html/ {{Dead link|date=December 2009}}</ref> | |
− | + | ==Ecosystems==<!— This section is linked from Nature —> | |
+ | [[File:View of loch lomond.JPG|thumb|left|[[Loch Lomond]] in Scotland forms a relatively isolated ecosystem. The fish community of this lake has remained unchanged over a very long period of time.<ref>{{cite journal | last=Adams | first=C.E. | title=The fish community of Loch Lomond, Scotland : its history and rapidly changing status | journal=Hydrobiologia | year=1994 | volume=290 | issue=1-3 | pages=91–102 | url=http://cat.inist.fr/?aModele=afficheN&cpsidt=3302548 | doi=10.1007/BF00008956 }}</ref>]] | ||
+ | [[File:Chicago Downtown Aerial View.jpg|thumb|An aerial view of a [[human ecosystem]]. Pictured is the city of [[Chicago]]]] | ||
− | + | {{Main|Ecology|Ecosystem}} | |
− | {{ | ||
− | |||
− | + | Ecosystems are composed of a variety of [[abiotic]] and [[Biotic component|biotic]] components that function in an interrelated way.<ref>{{cite web |last=Pidwirny |first=Michael |year=2006 |work=Fundamentals of Physical Geography (2nd Edition) |title=Introduction to the Biosphere: Introduction to the Ecosystem Concept |url=http://www.physicalgeography.net/fundamentals/9j.html |accessdate=September 28, 2006}}</ref> The structure and composition is determined by various environmental factors that are interrelated. Variations of these factors will initiate dynamic modifications to the ecosystem. Some of the more important components are: [[soil]], atmosphere, radiation from the [[sun]], water, and living organisms. | |
− | + | Central to the ecosystem concept is the idea that [[living organism]]s interact with every other element in their local [[environment (biophysical)|environment]]. Eugene Odum, a founder of ecology, stated: "Any unit that includes all of the organisms (ie: the "community") in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e.: exchange of materials between living and nonliving parts) within the system is an ecosystem."<ref name="Odum1971">Odum, EP (1971) Fundamentals of ecology, third edition, Saunders New York</ref> Within the ecosystem, species are connected and dependent upon one another in the [[food chain]], and exchange [[energy]] and [[matter]] between themselves as well as with their environment.<ref>{{cite web |last=Pidwirny |first=Michael |year=2006 |work=Fundamentals of Physical Geography (2nd Edition) |title=Introduction to the Biosphere: Organization of Life |url=http://www.physicalgeography.net/fundamentals/9d.html |accessdate=September 28, 2006}}</ref></blockquote> The human ecosystem concept is grounded in the deconstruction of the human/nature [[dichotomy]] and the premise that all species are ecologically integrated with each other, as well as with the abiotic constituents of their [[biotope]].{{Citation needed|date=February 2010}} | |
− | + | A smaller unit of size is called a [[microecosystem]]. For example, a microsystem can be a stone and all the life under it. A ''macroecosystem'' might involve a whole [[ecoregion]], with its [[drainage basin]].<ref>{{cite journal |last=Bailey |first=Robert G. |year=2004 |month=April |title=Identifying Ecoregion Boundaries |journal=Environmental Management |volume=34 |pmid=15883869 |issue=Supplement 1 |url=http://www.fs.fed.us/institute/news_info/Identifying_ecoregion_boundaries.pdf |format=PDF|doi=10.1007/s00267-003-0163-6 |pages=S14 }}</ref> | |
− | |||
− | |||
− | |||
− | + | ===Wilderness=== | |
− | + | [[Image:Biogradska suma.jpg|thumb|right|250px|[[Old-growth forest|Old growth]] [[European Beech]] forest in [[Biogradska Gora National Park]], [[Montenegro]].]] | |
+ | {{Main|Wilderness}} | ||
+ | '''Wilderness''' is generally defined as areas that have not been significantly modified by [[human]] activity. [http://www.wild.org/main/about/what-is-a-wilderness-area/ The WILD Foundation] goes into more detail, defining wilderness as: "The most intact, undisturbed wild natural areas left on our planet - those last truly wild places that humans do not control and have not developed with roads, pipelines or other industrial infrastructure." Wilderness areas can be found in preserves, estates, farms, conservation preserves, ranches, [[National Forest]]s, [[National Park]]s and even in [[urban area]]s along rivers, gulches or otherwise [[undeveloped area]]s. [http://www.wild.org/main/about/what-is-a-wilderness-area/ Wilderness areas] and protected [[parks]] are considered important for the survival of certain [[species]], ecological studies, [[Habitat conservation|conservation]], solitude, and [[recreation]]. Some nature writers believe wilderness areas are vital for the human spirit and creativity,<ref name="Man p155-157">No Man's Garden by Daniel B. Botkin p155-157</ref> and some [[Ecologist]]s consider wilderness areas to be an integral part of the planet's self-sustaining natural [[ecosystem]] (the [[biosphere]]). They may also preserve historic [[genetics|genetic]] traits and that they provide [[habitat]] for wild [[flora (plants)|flora]] and [[fauna (animals)|fauna]] that may be difficult to recreate in [[zoo]]s, [[arboretum]]s or [[laboratory|laboratories]]. | ||
− | == | + | ==Life== |
− | [[ | + | [[File:Malards in Golden Gate Park.jpg|thumb|left|250px|Female mallard and ducklings - [[reproduction]] is essential for continuing life]] |
− | + | {{Main|Life|Biology|Biosphere}} | |
− | + | Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by [[Organism|organization]], [[metabolism]], [[cell growth|growth]], [[adaptation]], response to [[stimulus (physiology)|stimuli]] and [[reproduction]].<ref>{{cite web | year = 2006 | url = http://www.calacademy.org/exhibits/xtremelife/what_is_life.php | title = Definition of Life | publisher = California Academy of Sciences | accessdate = 2007-01-07 }}</ref> Life may also be said to be simply the characteristic state of [[organism]]s. | |
− | + | Properties common to terrestrial organisms ([[plant]]s, [[animal]]s, [[fungi]], [[protist]]s, [[archaea]] and [[bacteria]]) are that they are cellular, carbon-and-water-based with complex organization, having a metabolism, a capacity to grow, respond to stimuli, and reproduce. An entity with these properties is generally considered life. However, not every definition of life considers all of these properties to be essential. Human-made [[Artificial life|analogs of life]] may also be considered to be life. | |
− | + | The [[biosphere]] is the part of Earth's outer shell – including land, surface rocks, water, air and the atmosphere – within which life occurs, and which [[Biology|biotic]] processes in turn alter or transform. From the broadest [[Geophysiology|geophysiological]] point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the [[lithosphere]] (rocks), [[hydrosphere]] (water), and [[atmosphere]] (air). Currently the entire Earth contains over 75 billion tons (150 ''trillion'' pounds or about 6.8 x 10<sup>13</sup> [[kilogram]]s) of [[biomass (ecology)|biomass]] (life), which lives within various environments within the biosphere.<ref>The figure "about one-half of one percent" takes into account the following (See, e.g., {{cite book |last=Leckie |first=Stephen |year=1999 |chapter=How Meat-centred Eating Patterns Affect Food Security and the Environment |chapterurl=http://www.idrc.ca/en/ev-30610-201-1-DO_TOPIC.html |title=For hunger-proof cities : sustainable urban food systems |publisher=International Development Research Centre |location=Ottawa |isbn=0-88936-882-1}}, which takes global average weight as 60 kg.), the total human biomass is the average weight multiplied by the current human population of approximately 6.5 billion (see, ''e.g.'', {{cite web |title=World Population Information |url=http://www.census.gov/ipc/www/world.html |accessdate=September 28, 2006 |publisher=U.S. Census Bureau}}): Assuming 60–70 kg to be the average human mass (approximately 130–150 [[pound (mass)|lb]] on the average), an approximation of total global human mass of between 390 billion (390×10<sup>9</sup>) and 455 billion kg (between 845 billion and 975 billion lb, or about 423 million–488 million [[short ton]]s). The total biomass of all kinds on earth is estimated to be in excess of 6.8 x 10<sup>13</sup> kg (75 billion short tons). By these calculations, the portion of total biomass accounted for by humans would be very roughly 0.6%.</ref> | |
− | + | Over nine-tenths of the total biomass on Earth is plant life, on which animal life depends very heavily for its existence.<ref>{{cite web |first=Peter V. |last=Sengbusch |title=The Flow of Energy in Ecosystems - Productivity, Food Chain, and Trophic Level |work=Botany online |publisher=University of Hamburg Department of Biology |url=http://www.biologie.uni-hamburg.de/b-online/e54/54c.htm |accessdate=September 23, 2006}}</ref> More than 2 million species of plant and animal life have been identified to date,<ref>{{cite web |last=Pidwirny |first=Michael |year=2006 |work=Fundamentals of Physical Geography (2nd Edition) |title=Introduction to the Biosphere: Species Diversity and Biodiversity |url=http://www.physicalgeography.net/fundamentals/9h.html |accessdate=September 23, 2006}}</ref> and estimates of the actual number of existing species range from several million to well over 50 million.<ref>{{cite web |url=http://faculty.plattsburgh.edu/thomas.wolosz/howmanysp.htm |title=How Many Species are There? |work=Extinction Web Page Class Notes |accessdate=September 23, 2006}}</ref><ref>"Animal." World Book Encyclopedia. 16 vols. Chicago: World Book, 2003. This source gives an estimate of from 2 to 50 million.</ref><ref>{{cite web |url=http://www.sciencedaily.com/releases/2003/05/030526103731.htm |title=Just How Many Species Are There, Anyway? |publisher=Science Daily |year=2003 |month=May |accessdate=September 26, 2006 }}</ref> The number of individual species of life is constantly in some degree of flux, with new species appearing and others ceasing to exist on a continual basis.<ref>{{cite web |last=Withers |first=Mark A. |coauthors=et al. |title=Changing Patterns in the Number of Species in North American Floras |work=Land Use History of North America |url=http://biology.usgs.gov/luhna/chap4.html |year=1998 |accessdate=September 26, 2006 }} Website based on the contents of the book: {{cite book |editor=Sisk, T.D., ed. |year=1998 |title=Perspectives on the land use history of North America: a context for understanding our changing environment |publisher=U.S. Geological Survey, Biological Resources Division |id=USGS/BRD/BSR-1998-0003 |edition=Revised September 1999 }}</ref><ref>{{cite web |title=Tropical Scientists Find Fewer Species Than Expected |url=http://www.sciencedaily.com/releases/2002/04/020425072847.htm |year=2002 |month=April |publisher=Science Daily |accessdate=September 27, 2006 }}</ref> The total number of species is presently in rapid decline.<ref>{{cite journal |last=Bunker |first=Daniel E. |coauthors=et al. |title=Species Loss and Aboveground Carbon Storage in a Tropical Forest |url=http://www.sciencemag.org/cgi/content/abstract/310/5750/1029 |journal=Science |year=2005 |month=November |volume=310 |issue=5750 |pages=1029–31 |doi=10.1126/science.1117682 |pmid=16239439 }}</ref><ref>{{cite journal |last=Wilcox |first=Bruce A. |title=Amphibian Decline: More Support for Biocomplexity as a Research Paradigm |journal=EcoHealth |year=2006 |month=March |volume=3 |issue=1 |url=http://www.springerlink.com/content/810227460032m460/ |doi=10.1007/s10393-005-0013-5 | pages = 1}}</ref><ref>{{cite book |editor=Clarke, Robin, Robert Lamb, Dilys Roe Ward eds. |year=2002 |title= Global environment outlook 3 : past, present and future perspectives |chapter=Decline and loss of species |chapterurl=http://www.grida.no/geo/geo3/english/221.htm |publisher=Nairobi, Kenya : UNEP |location=London; Sterling, VA |isbn=92-807-2087-2}}</ref> | |
− | [[ | + | ===Evolution=== |
+ | [[Image:Amazon Manaus forest.jpg|thumb|right|300px|An area of the [[Amazon Rainforest]] in [[Brazil]]. The [[tropical rainforest]]s of [[South America]] contain the largest [[biodiversity|diversity]] of species on [[Earth]].<ref>http://earthobservatory.nasa.gov/Newsroom/view.php?id=28907</ref><ref>http://www.sciencedaily.com/releases/2005/12/051205163236.htm</ref>]] | ||
+ | {{Main|Evolution}} | ||
+ | Life is only known to exist on the planet Earth.(cf [[Astrobiology]]) The [[origin of life]] is still a poorly understood process, but it is thought to have occurred about 3.9 to 3.5 billion years ago during the [[hadean]] or [[archean]] eons on a primordial earth that had a substantially different environment than is found at present.<ref name=Line>{{cite journal | author = Line M | title = The enigma of the origin of life and its timing | url=http://mic.sgmjournals.org/cgi/content/full/148/1/21?view=long&pmid=11782495 | journal = Microbiology | volume = 148 | issue = Pt 1 | pages = 21–7 | date=1 January 2002| pmid = 11782495 }}</ref> These life forms possessed the basic traits of self-replication and inheritable traits. Once life had appeared, the process of [[evolution]] by [[natural selection]] resulted in the development of ever-more diverse life forms. | ||
− | + | Species that were unable to adapt to the changing environment and competition from other life forms became extinct. However, the [[fossil]] record retains evidence of many of these older species. Current fossil and [[DNA]] evidence shows that all existing species can trace a continual ancestry back to the first primitive life forms.<ref name=Line/> | |
− | {{ | + | The advent of [[photosynthesis]] in very basic forms of plant life worldwide allowed the sun's energy to be harvested to create conditions allowing for more complex life.{{Citation needed|date=April 2010}} The resultant [[oxygen]] accumulated in the atmosphere and gave rise to the [[ozone layer]]. The incorporation of smaller cells within larger ones resulted in the [[endosymbiotic theory|development of yet more complex cells]] called [[eukaryotes]].<ref>{{cite journal |first=L. V. |last=Berkner |coauthors=L. C. Marshall |year=1965 |month=May |title=On the Origin and Rise of Oxygen Concentration in the Earth's Atmosphere |journal=Journal of the Atmospheric Sciences |volume=22 |issue=3 |pages=225–261 |url=http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0469(1965)022%3C0225:OTOARO%3E2.0.CO%3B2 |doi=10.1175/1520-0469(1965)022<0225:OTOARO>2.0.CO;2 }}</ref> Cells within colonies became increasingly specialized, resulting in true multicellular organisms. With the ozone layer absorbing harmful [[ultraviolet radiation]], life colonized the surface of Earth. |
− | == | + | ===Microbes=== |
− | [[Image: | + | [[Image:Yellow mite (Tydeidae) Lorryia formosa 2 edit.jpg|thumb|right|140px|left|A microscopic mite ''[[Mite|Lorryia formosa]]''.]] |
− | + | {{Main|Microbe}} | |
− | + | The first form of life to develop on the Earth were microbes, and they remained the only form of life on the planet until about a billion years ago when multi-cellular organisms began to appear.<ref>{{cite journal | | |
+ | author = Schopf J | title = Disparate rates, differing fates: tempo and mode of evolution changed from the Precambrian to the Phanerozoic. | url=http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=44277&blobtype=pdf | journal = Proc Natl Acad Sci USA | volume = 91 | issue = 15 | format=PDF | pages = S14 | year = 1994 | pmid = 8041691 | doi = 10.1073/pnas.91.15.6735 | | ||
+ | pmc = 44277 | ||
+ | }}</ref> Microorganisms are single-celled organisms that are generally [[microscopic]], and smaller than the human eye can see. They include [[Bacteria]], [[Fungi]], [[Archaea]] and [[Protista]]. | ||
− | + | These life forms are found in almost every location on the Earth where there is liquid water, including the interior of rocks within the planet.<ref>{{cite journal | author = Szewzyk U, Szewzyk R, Stenström T | title = Thermophilic, anaerobic bacteria isolated from a deep borehole in granite in Sweden. | doi= 10.1073/pnas.91.5.1810 | journal = Proc Natl Acad Sci USA | volume = 91 | issue = 5 | pages = 1810–3 | year = 1994 | pmid = 11607462 | pmc = 43253}}</ref> | |
+ | Their reproduction is both rapid and profuse. The combination of a high mutation rate and a [[horizontal gene transfer]]<ref>{{cite journal | author = Wolska K | title = Horizontal DNA transfer between bacteria in the environment. | journal = Acta Microbiol Pol | volume = 52 | issue = 3 | pages = 233–43 | year = 2003 | pmid = 14743976}}</ref> ability makes them highly adaptable, and able to survive in new environments, including [[outer space]].<ref>{{cite journal | author = Horneck G | title = Survival of microorganisms in space: a review. | journal = Adv Space Res | volume = 1 | issue = 14 | pages = 39–48 | year = 1981 | pmid = 11541716 | doi = 10.1016/0273-1177(81)90241-6}}</ref> They form an essential part of the planetary ecosystem. However some microorganisms are [[pathogenic]] and can post health risk to other organisms. | ||
− | + | ===Plants and animals=== | |
+ | [[Image:Plants.jpg|thumb|left|200px|<center>A selection of diverse [[plant species]]</center>]] | ||
− | + | {{Main|Plants|Animals}} | |
− | + | {{See also|Botany|Fauna|Biology}} | |
− | + | Originally [[Aristotle]] divided all living things between plants, which generally do not move fast enough for humans to notice, and animals. In [[Carolus Linnaeus|Linnaeus]]' system, these became the [[kingdom (biology)|kingdoms]] [[Vegetabilia]] (later [[Plantae]]) and [[Animal]]ia. Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the [[fungus|fungi]] and several groups of [[alga]]e were removed to new kingdoms. However, these are still often considered plants in many contexts. Bacterial life is sometimes included in flora,<ref>{{cite web |title=flora |url=http://webster.com/cgi-bin/dictionary?va=flora |work=Merriam-Webster Online Dictionary |publisher=Merriam-Webster |accessdate=September 27, 2006 }}</ref><ref>{{cite book |year=1998 |title=Status and Trends of the Nation's Biological Resources |chapter=Glossary |chapterurl=http://biology.usgs.gov/s+t/SNT/noframe/zy198.htm#F |publisher=Department of the Interior, Geological Survey |location=Reston, VA |id=SuDocs No. I 19.202:ST 1/V.1-2}}</ref> and some classifications use the term ''bacterial flora'' separately from ''plant flora''. | |
− | |||
− | |||
− | |||
− | + | Among the many ways of classifying [[plants]] are by regional [[flora]]s, which, depending on the purpose of study, can also include ''fossil flora'', remnants of plant life from a previous era. People in many regions and countries take great pride in their individual arrays of characteristic flora, which can vary widely across the globe due to differences in climate and [[terrain]]. | |
− | + | Regional floras commonly are divided into categories such as ''native flora'' and ''agricultural and garden flora'', the lastly mentioned of which are intentionally grown and cultivated. Some types of "native flora" actually have been introduced centuries ago by people migrating from one region or continent to another, and become an integral part of the native, or natural flora of the place to which they were introduced. This is an example of how human interaction with nature can blur the boundary of what is considered nature. | |
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− | |||
− | + | Another category of plant has historically been carved out for ''weeds''. Though the term has fallen into disfavor among [[botanist]]s as a formal way to categorize "useless" plants, the informal use of the word "weeds" to describe those plants that are deemed worthy of elimination is illustrative of the general tendency of people and societies to seek to alter or shape the course of nature. Similarly, animals are often categorized in ways such as ''domestic'', ''farm animals'', ''wild animals'', ''pests'', etc. according to their relationship to human life. | |
− | + | [[image:Animal diversity October 2007.jpg|thumb|right|230px|<center>There are many [[animal species]] on the planet.</center>]] | |
+ | [[Animal]]s as a category have several characteristics that generally set them apart from other living things, though this is not traced by scientists to having legs or wings instead of roots and leaves.{{Citation needed|date=April 2010}} Animals are [[eukaryote|eukaryotic]] and usually [[multicellular]] (although see [[Myxozoa]]), which separates them from [[bacteria]], [[archaea]] and most [[protist]]s. They are [[heterotroph]]ic, generally digesting food in an internal chamber, which separates them from [[plant]]s and [[alga]]e. They are also distinguished from plants, algae, and [[fungus|fungi]] by lacking [[cell wall]]s. | ||
− | + | With a few exceptions, most notably the [[sea sponge|sponges]] (Phylum Porifera), animals have bodies differentiated into separate [[biological tissue|tissues]].{{Citation needed|date=April 2010}} These include [[muscle]]s, which are able to contract and control locomotion, and a [[nervous system]], which sends and processes signals. There is also typically an internal [[digestion|digestive]] chamber. The eukaryotic cells possessed by all animals are surrounded by a characteristic extracellular matrix composed of [[collagen]] and elastic [[glycoprotein]]s. This may be calcified to form structures like [[Animal shell|shells]], [[bone]]s, and [[spicule]]s, a framework upon which cells can move about and be reorganized during development and maturation, and which supports the complex anatomy required for mobility. | |
− | == | + | ==Human interrelationship== |
− | [[ | + | [[File:Na Pali Coast - Kauai.jpg|thumb|right|250px|Despite their natural beauty, the secluded valleys along the [[Na Pali Coast]] in [[Hawaii]] are heavily modified by introduced [[invasive species]] such as [[She-oak]].]] |
− | + | [[File:Dendrarium Sochi Mauritanian arbour.jpg|thumb|250px|right|[[Sochi]] dendrarium is an example of confluence of "natural" and a "made" environment]] | |
− | + | Although humans currently comprise only a minuscule proportion of the total living biomass on Earth, the human effect on nature is disproportionately large. Because of the extent of human influence, the boundaries between what humans regard as nature and "made environments" is not clear cut except at the extremes. Even at the extremes, the amount of natural environment that is free of discernible human influence is presently diminishing at an increasingly rapid pace. | |
− | The | + | The development of technology by the human race has allowed the greater exploitation of natural resources and has helped to alleviate some of the risk from natural hazards. In spite of this progress, however, the fate of human [[civilization]] remains closely linked to changes in the environment. There exists a highly complex feedback loop between the use of advanced technology and changes to the environment that are only slowly becoming understood.<ref>{{cite news | title=Feedback Loops In Global Climate Change Point To A Very Hot 21st Century | publisher=Science Daily | date=May 22, 2006 | url=http://www.lbl.gov/Science-Articles/Archive/ESD-feedback-loops.html | accessdate=2007-01-07 }}</ref> Man-made threats to the Earth's natural environment include [[pollution]], [[deforestation]], and disasters such as oil spills. Humans have contributed to the [[extinction]] of many plants and animals. |
− | + | Humans employ nature for both leisure and economic activities. The acquisition of natural resources for industrial use remains the primary component of the world's economic system. {{Citation needed|date=April 2010}} Some activities, such as [[hunting]] and [[fishing]], are used for both sustenance and leisure, often by different people. [[Agriculture#History|Agriculture]] was first adopted around the [[9th millennium B.C.E.]]. Ranging from food production to [[energy]], nature influences economic wealth. | |
− | + | Although early humans gathered uncultivated plant materials for food and employed the medicinal properties of vegetation for healing,<ref>{{cite web | url = http://www.nps.gov/plants/medicinal/plants.htm | title = Plant Conservation Alliance - Medicinal Plant Working Groups Green Medicine | publisher = US National Park Services |accessdate=September 23, 2006}}</ref> most modern human use of plants is through agriculture. The clearance of large tracts of land for crop growth has led to a significant reduction in the amount available of forestation and wetlands, resulting in the loss of habitat for many plant and animal species as well as increased erosion.<ref>{{cite web | last = Oosthoek | first = Jan | year = 1999 | url = http://www.eh-resources.org/philosophy.html | title = Environmental History: Between Science & Philosophy | publisher = Environmental History Resources | accessdate = 2006-12-01 }}</ref> | |
− | == | + | ===Aesthetics and beauty=== |
− | [[ | + | [[File:504px-Pinguiculagrandiflora1web.jpg|thumb|left|''[[Pinguicula grandiflora]]'', commonly known as a [[Butterwort]]]] |
− | Beauty in nature | + | [[Beauty]] in nature has historically been a prevalent theme in art and books, filling large sections of libraries and bookstores. That nature has been depicted and celebrated by so much [[art]], [[photography]], [[poetry]] and other literature shows the strength with which many people associate nature and beauty. Reasons why this association exists, and what the association consists of, is studied by the branch of philosophy called [[aesthetics]]. Beyond certain basic characteristics that many philosophers agree about to explain what is seen as beautiful, the opinions are virtually endless.<ref>For an example of a range of opinions, see: {{cite web |url=http://www.wilderness.org/Library/Documents/Beauty_Quotes.cfm |title=On the Beauty of Nature |publisher=The Wilderness Society |accessdate=September 29, 2006 }} and [[Ralph Waldo Emerson]]'s analysis of the subject: {{cite book |last=Emerson |first=Ralph Waldo |year=1849 |title=Nature; Addresses and Lectures |chapter=Beauty |chapterurl=http://www.emersoncentral.com/beauty.htm}}</ref> Nature and wildness have been important subjects in various [[epoch]]s of world history. An early tradition of [[landscape art]] began in [[China]] during the [[Tang Dynasty art|Tang Dynasty]] (618-907). The tradition of representing nature ''as it is'' became one of the aims of [[Chinese painting]] and was a significant influence in Asian art. |
− | + | Although natural wonders are celebrated in the [[Psalms]] and the [[Book of Job]], [[wilderness]] portrayals in art became more prevalent in the 1800s, especially in the works of the [[Romantic movement]]. [[Kingdom of Great Britain|British]] artists [[John Constable]] and [[JMW Turner]] turned their attention to capturing the beauty of the natural world in their paintings. Before that, paintings had been primarily of religious scenes or of human beings. [[William Wordsworth]]'s poetry described the wonder of the natural world, which had formerly been viewed as a threatening place. Increasingly the valuing of nature became an aspect of Western culture.<ref name=History>[http://www.spacesfornature.org/greatspaces/conservation.html History of Conservation] BC Spaces for Nature. Accessed: May 20, 2006.</ref> This artistic movement also coincided with the [[Transcendentalism|Transcendentalist movement]] in the Western world. A common classical idea of beautiful art involves the word [[mimesis]], the imitation of nature. Also in the realm of ideas about beauty in nature is that the perfect is implied through symmetry, equal division, and other perfect mathematical [[forms]] and notions. {{Citation needed|date=April 2010}} | |
− | + | ==Matter and energy== | |
− | [[ | + | [[File:Hydrogen Density Plots.png|thumb|left|200px|The first few [[hydrogen atom]] [[electron orbital]]s shown as cross-sections with color-coded probability density]] |
− | + | {{Main|Matter|Energy}} | |
− | {{ | + | {{See also|Chemistry|Physics}} |
− | Some fields of [[science]] see nature as matter in motion, obeying certain laws of nature which science seeks to understand. For this reason the most fundamental science is generally understood to be "[[physics]]"& | + | Some fields of [[science]] see nature as matter in motion, obeying certain laws of nature which science seeks to understand. For this reason the most fundamental science is generally understood to be "[[physics]]" – the name for which is still recognizable as meaning that it is the study of nature. |
− | Matter is commonly defined as the substance of which physical objects are composed. It constitutes the [[observable universe]]. | + | Matter is commonly defined as the substance of which physical objects are composed. It constitutes the [[observable universe]]. The visible components of the universe are now believed to compose only 4 percent of the total mass. The remainder is believed to consist of 23 percent cold [[dark matter]] and 73 percent [[dark energy]].<ref>{{cite web |url=http://map.gsfc.nasa.gov/m_mm/mr_limits.html |title=Some Theories Win, Some Lose |work=[[WMAP]] Mission: First Year Results |publisher=[[NASA]] |accessdate=29 2006 }}</ref> The exact nature of these components is still unknown and is currently under intensive investigation by physicists. |
− | The behavior of matter and energy throughout the | + | The behavior of matter and energy throughout the observable universe appears to follow well-defined [[physical law]]s. These laws have been employed to produce [[Physical cosmology|cosmological]] models that successfully explain the structure and the evolution of the universe we can observe. The mathematical expressions of the laws of physics employ a set of twenty [[physical constant]]s<ref>{{cite web | last = Taylor | first = Barry N. | year = 1971 | url = http://www.physics.nist.gov/cuu/Constants/introduction.html | title = Introduction to the constants for nonexperts | publisher = National Institute of Standards and Technology | accessdate = 2007-01-07 |
+ | }}</ref> that appear to be static across the observable universe.<ref>{{cite journal | author=D. A. Varshalovich, A. Y. Potekhin, A. V. Ivanchik | title=Testing cosmological variability of fundamental constants | journal=AIP Conference Proceedings | year=2000 | volume=506 | pages=503 | url=http://arxiv.org/abs/physics/0004062 | doi=10.1063/1.1302777 }}</ref> The values of these constants have been carefully measured, but the reason for their specific values remains a mystery. | ||
− | {{ | + | ==Beyond Earth== |
+ | [[File:Planets2008.jpg|thumb|[250px|[[Planet]]s and [[dwarf planet]]s of the [[Solar System]] ''(Sizes to scale, distances not to scale)'']] | ||
+ | [[File:Hubble ultra deep field high rez edit1.jpg|thumb|200px|The deepest visible-light image of the [[universe]] from the [[Hubble Ultra Deep Field]] telescope]] | ||
+ | [[File:NGC 4414 (NASA-med).jpg|thumb|200px|'''[[NGC 4414]]''' is a spiral galaxy in the constellation [[Coma Berenices]] about 56,000 [[light year]]s in diameter and approximately 60 million light years from [[Earth]]]] | ||
+ | {{Main|Outer space|Universe|Extraterrestrial life}} | ||
− | + | '''Outer space''', also simply called ''space'', refers to the relatively empty regions of the [[universe]] outside the [[celestial body's atmosphere|atmospheres]] of celestial bodies. ''Outer'' space is used to distinguish it from [[airspace]] (and terrestrial locations). There is no discrete boundary between the [[Earth's atmosphere]] and space, as the atmosphere gradually attenuates with increasing altitude. Outer space within the [[solar system]] is called [[interplanetary space]], which passes over into [[interstellar medium|interstellar space]] at what is known as the [[heliopause]]. | |
− | |||
− | |||
− | '''Outer space''', also simply called ''space'', refers to the relatively empty regions of the [[universe]] outside the [[celestial body's atmosphere| | ||
− | Outer space is certainly spacious, but it is far from empty. | + | Outer space is certainly spacious, but it is far from empty. {{Citation needed|date=April 2010}} Outer space is sparsely filled with several dozen types of [[organic chemistry|organic]] [[molecule]]s discovered to date by [[rotational spectroscopy|microwave spectroscopy]], [[cosmic microwave background radiation|blackbody radiation]] left over from the [[big bang]] and the origin of the universe, and [[cosmic ray]]s, which include [[ion]]ized [[atomic nucleus|atomic nuclei]] and various [[subatomic particle]]s. There is also some gas, [[Plasma (physics)|plasma]] and [[dust]], and small [[meteor]]s. Additionally, there are signs of human life in outer space today, such as material left over from previous manned and unmanned launches which are a potential hazard to spacecraft. Some of this [[space debris|debris]] re-enters the atmosphere periodically. |
− | Although the planet Earth is currently the only known body within the solar system to support life, current evidence suggests that in the distant past the planet [[Mars]] possessed bodies of liquid water on the surface.<ref>{{cite journal | | + | Although the planet Earth is currently the only known body within the solar system to support life, current evidence suggests that in the distant past the planet [[Mars]] possessed bodies of liquid water on the surface.<ref>{{cite journal | last = Bibring | first = J | coauthors = Langevin Y, Mustard J, Poulet F, Arvidson R, Gendrin A, Gondet B, Mangold N, Pinet P, Forget F, Berthé M, Bibring J, Gendrin A, Gomez C, Gondet B, Jouglet D, Poulet F, Soufflot A, Vincendon M, Combes M, Drossart P, Encrenaz T, Fouchet T, Merchiorri R, Belluci G, Altieri F, Formisano V, Capaccioni F, Cerroni P, Coradini A, Fonti S, Korablev O, Kottsov V, Ignatiev N, Moroz V, Titov D, Zasova L, Loiseau D, Mangold N, Pinet P, Douté S, Schmitt B, Sotin C, Hauber E, Hoffmann H, Jaumann R, Keller U, Arvidson R, Mustard J, Duxbury T, Forget F, Neukum G | title = Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data | journal = Science | volume = 312 | issue = 5772 | pages = 400–4 | year = 2006 | pmid = 16627738 | doi = 10.1126/science.1122659}}</ref> For a brief period in Mars' history, it may have also been capable of forming life. At present though, most of the water remaining on Mars is frozen. |
− | If life exists at all on Mars, it is most likely to be located underground where liquid water can still exist.<ref> | + | If life exists at all on Mars, it is most likely to be located underground where liquid water can still exist.<ref>{{cite web | first = Tariq | last = Malik | date = 2005-03-08 | url = http://www.msnbc.msn.com/id/7129347/ | title = Hunt for Mars life should go underground | publisher = The Brown University News Bureau |accessdate=September 4, 2006}}</ref> |
− | Conditions on the other terrestrial planets, [[Mercury (planet)|Mercury]] and [[Venus]], | + | Conditions on the other terrestrial planets, [[Mercury (planet)|Mercury]] and [[Venus]], appear to be too harsh to support life as we know it. {{Citation needed|date=April 2010}} But it has been conjectured that [[Europa (moon)|Europa]], the fourth-largest moon of [[Jupiter]], may possess a sub-surface ocean of liquid water and could potentially host life.<ref>{{cite web | author = Scott Turner | date = 1998-03-02 | url = http://www2.jpl.nasa.gov/galileo/news8.html | title = Detailed Images From Europa Point To Slush Below Surface | publisher = The Brown University News Bureau |accessdate=September 28, 2006}}</ref> |
− | Recently, the team of [[Stéphane Udry]] have discovered a new planet named [[Gliese 581 | + | Recently, the team of [[Stéphane Udry]] have discovered a new planet named [[Gliese 581 g]], which is an [[extrasolar planet]] orbiting the [[red dwarf]] [[star]] [[Gliese 581]]. {{Citation needed|date=April 2010}} Gliese 581 g appears to lie in the [[habitable zone]] of space surrounding the [[star]], and therefore could possibly host [[life]] as we know it. |
− | {{ | + | ==See also== |
+ | {{Wikipedia-Books}} | ||
+ | {{Portal box|Environment|Ecology|Earth sciences|Weather|Astronomy}} | ||
− | |||
'''Science:''' | '''Science:''' | ||
* [[Natural history]] | * [[Natural history]] | ||
− | |||
* [[Natural science]] | * [[Natural science]] | ||
+ | * [[Natural landscape]] | ||
'''Philosophy:''' | '''Philosophy:''' | ||
+ | * [[Mother Nature]] | ||
* [[Nature (philosophy)]] | * [[Nature (philosophy)]] | ||
− | + | * [[Naturalism (philosophy)]]: any of several philosophical stances, typically those descended from [[Materialism]] and [[Pragmatism]] that do not distinguish the supernatural from nature. {{Citation needed|date=April 2010}} This includes the ''methodological naturalism'' of natural science, which makes the [[methodology|methodological]] assumption that [[observation|observable]] events in nature are explained only by natural causes, without assuming either the existence or non-existence of the supernatural. | |
− | * [[Naturalism (philosophy)]]: | + | * [[Balance of nature (biological fallacy)]]: A discredited concept of natural equilibrium in predator:prey dynamics. |
+ | {{Col-begin}} | ||
+ | {{Col-1-of-2}} | ||
'''Media:''' | '''Media:''' | ||
− | * ''[[Nature (Emerson)|Nature]]'', by [[Ralph Waldo Emerson]] | + | *''[[Natural History (Pliny)|Natural History]]'', by [[Pliny the Elder]] |
− | * ''[[Nature (journal)|Nature]]'', a prominent scientific journal | + | *''[[Nature (Emerson)|Nature]]'', by [[Ralph Waldo Emerson]] |
− | * ''[[ | + | *''[[Nature (journal)|Nature]]'', a prominent scientific journal |
− | * [[Nature (TV series)]] | + | *''[[National Wildlife Magazine]]'', publication of the National Wildlife Federation |
− | + | *[[Nature (TV series)]] | |
+ | {{Col-2-of-2}} | ||
'''Organizations:''' | '''Organizations:''' | ||
− | * [[The Nature Conservancy]] | + | *[[The Nature Conservancy]] |
− | * [[Nature Detectives]] | + | *[[Nature Detectives]] |
+ | {{col-end}} | ||
− | ==Notes== | + | ==Notes and references== |
− | + | [[Image:Mountains Tolima.jpeg|right|thumb|[[Landscape]] photograph of Tolima Colombia.]] | |
− | + | [[File:Archangelsk taiga.JPG|right|thumb|[[Taiga]] forest in winter, [[Arkhangelsk Oblast]], [[Russia]].]] | |
− | + | [[Image:Top of Atmosphere.jpg|right|thumb|[[Atmosphere|Atmospheric]] gases scatter blue wavelengths of visible light more than other wavelengths, giving the [[Earth]]’s visible edge a blue halo. Credit: [[NASA]]'s Earth Observatory.]] | |
+ | [[Image:Desertisland.jpg|thumb|right|A [[desert island|deserted island]] in [[Palau]].]] | ||
+ | [[Image:IMG 1977.JPG|thumb|right|Two Giant Sequoias, [[Sequoia National Park]]. Note the large fire scar at the base of the right-hand tree; fires do not kill the trees but do remove competing thin-barked species, and aid Giant Sequoia regeneration.]] | ||
+ | [[Image:Willow Creek, Trout Creek Mountains, Oregon.jpg|thumb|right|A [[Riparian zone]] along Trout Creek in the Trout Creek Mountains; part of the Burns Bureau of [[Land Management]] District in southeastern [[Oregon]].]] | ||
+ | {{Reflist}} | ||
− | == External links == | + | ==External links== |
− | + | {{sisterlinks}} | |
− | {{sisterlinks | + | *[http://www.nature.com/nature/index.html Nature Journal - Weekly journal of science]. |
− | *[http:// | + | *[http://www.wild.org The WILD Foundation]. |
− | * [http://www. | + | *[http://www.bbc.co.uk/sn/ BBC - Science and Nature]. |
− | * [http://www. | + | *[http://ec.europa.eu/environment/nature/index_en.htm European Commission - Nature and Biodiversity homepage]. |
− | * [http://www. | + | *[http://www.nature.org/ The Nature Conservancy] |
+ | *[http://www.science.gov/browse/w_123.htm Science.gov - Environment & Environmental Quality]. | ||
+ | *[http://www.wallpapers3.com/en/wallpapers-nature.html wallpapers nature]. | ||
+ | *[http://www.naturewatch.wikia.com/wiki/NatureWatch_Wiki NatureWatch - Wiki for documenting biodiversity (german)] | ||
+ | *[http://eng.me.go.kr/docs/sub2/policy_view.html?topmenu=C&cat=240&class=13 Ministry of Environment Republic of Korea - Nature] | ||
+ | {{Physical Earth}} | ||
{{Nature nav}} | {{Nature nav}} | ||
+ | {{Natural sciences-footer}} | ||
+ | {{Environmental science}} | ||
+ | {{Biology-footer}} | ||
+ | |||
+ | {{Good article}} | ||
+ | |||
+ | [[Category:Nature| ]] | ||
+ | [[Category:Environmental science]] | ||
+ | |||
+ | {{Link GA|zh}} | ||
+ | {{Link FA|ca}} | ||
+ | |||
+ | [[ar:طبيعة]] | ||
+ | [[an:Naturaleza]] | ||
+ | [[ast:Natura]] | ||
+ | [[az:Təbiət]] | ||
+ | [[bn:প্রকৃতি]] | ||
+ | [[zh-min-nan:Chū-jiân]] | ||
+ | [[be:Прырода]] | ||
+ | [[be-x-old:Прырода]] | ||
+ | [[bs:Priroda]] | ||
+ | [[bg:Природа]] | ||
+ | [[ca:Natura]] | ||
+ | [[cv:Çутçанталăк]] | ||
+ | [[cs:Příroda]] | ||
+ | [[cy:Natur]] | ||
+ | [[da:Natur]] | ||
+ | [[de:Natur]] | ||
+ | [[et:Loodus]] | ||
+ | [[el:Φύση]] | ||
+ | [[es:Naturaleza]] | ||
+ | [[eo:Naturo]] | ||
+ | [[eu:Natura]] | ||
+ | [[fa:طبیعت]] | ||
+ | [[fr:Nature]] | ||
+ | [[gl:Natureza]] | ||
+ | [[ko:자연]] | ||
+ | [[hy:Բնություն]] | ||
+ | [[hi:प्रकृति]] | ||
+ | [[hr:Priroda]] | ||
+ | [[io:Naturo]] | ||
+ | [[id:Alam]] | ||
+ | [[ia:Natura]] | ||
+ | [[os:Æрдз]] | ||
+ | [[is:Náttúra]] | ||
+ | [[it:Natura]] | ||
+ | [[he:טבע]] | ||
+ | [[jv:Alam]] | ||
+ | [[kn:ನಿಸರ್ಗ]] | ||
+ | [[krc:Табигъат]] | ||
+ | [[ka:ბუნება]] | ||
+ | [[lbe:ТIабиаьт]] | ||
+ | [[la:Natura]] | ||
+ | [[lv:Daba]] | ||
+ | [[lb:Natur]] | ||
+ | [[lt:Gamta]] | ||
+ | [[mk:Природа]] | ||
+ | [[mg:Zavaboary]] | ||
+ | [[ml:പ്രകൃതി]] | ||
+ | [[mr:निसर्ग]] | ||
+ | [[ms:Alam semula jadi]] | ||
+ | [[mwl:Natureza]] | ||
+ | [[mn:Байгаль]] | ||
+ | [[nah:Yeliztli]] | ||
+ | [[nl:Natuur (kosmos)]] | ||
+ | [[new:इयऱ्कै (सन् २००३या संकिपा)]] | ||
+ | [[ja:自然]] | ||
+ | [[no:Natur]] | ||
+ | [[nn:Natur]] | ||
+ | [[mhr:Йыр улшо пӱртӱс]] | ||
+ | [[uz:Tabiat]] | ||
+ | [[pnb:نیچر]] | ||
+ | [[pl:Natura]] | ||
+ | [[pt:Natureza]] | ||
+ | [[ro:Natură]] | ||
+ | [[qu:Sallqa pacha]] | ||
+ | [[ru:Природа]] | ||
+ | [[sah:Айылҕа]] | ||
+ | [[sq:Natyra]] | ||
+ | [[scn:Natura (cumplessu naturali)]] | ||
+ | [[simple:Nature]] | ||
+ | [[sk:Príroda]] | ||
+ | [[sl:Narava]] | ||
+ | [[ckb:سروشت]] | ||
+ | [[sr:Природа]] | ||
+ | [[sh:Priroda]] | ||
+ | [[su:Alam]] | ||
+ | [[fi:Luonto]] | ||
+ | [[sv:Natur]] | ||
+ | [[tl:Kalikasan]] | ||
+ | [[ta:இயற்கை]] | ||
+ | [[tt:Табигать]] | ||
+ | [[th:ธรรมชาติ]] | ||
+ | [[tg:Табиат]] | ||
+ | [[tr:Doğa]] | ||
+ | [[uk:Природа]] | ||
+ | [[ur:فطرت]] | ||
+ | [[za:Mbwnnamh]] | ||
+ | [[vi:Tự nhiên]] | ||
+ | [[war:Libong]] | ||
+ | [[yi:נאטור]] | ||
+ | [[yo:Àdánidá]] | ||
+ | [[bat-smg:Gamta]] | ||
+ | [[zh:自然]] | ||
+ | |||
[[Category:Life sciences]] | [[Category:Life sciences]] | ||
− | {{credits|Nature| | + | {{credits|Nature|407503540}} |
Revision as of 19:22, 13 January 2011
- This article is about the physical universe. For other uses of the term, see Nature (disambiguation).
- "Natural" and "Natural World" redirect here. For other uses, see Natural (disambiguation).
Nature, in the broadest sense, is equivalent to the natural world, physical world, or material world. "Nature" refers to the phenomena of the physical world, and also to life in general. It ranges in scale from the subatomic to the cosmic.
The word nature is derived from the Latin word natura, or "essential qualities, innate disposition", and in ancient times, literally meant "birth".[1] Natura was a Latin translation of the Greek word physis (φύσις), which originally related to the intrinsic characteristics that plants, animals, and other features of the world develop of their own accord.[2][3] The concept of nature as a whole, the physical universe, is one of several expansions of the original notion; it began with certain core applications of the word φύσις by pre-Socratic philosophers, and has steadily gained currency ever since. This usage was confirmed during the advent of modern scientific method in the last several centuries.[4][5]
Within the various uses of the word today, "nature" may refer to the general realm of various types of living plants and animals, and in some cases to the processes associated with inanimate objects–the way that particular types of things exist and change of their own accord, such as the weather and geology of the Earth, and the matter and energy of which all these things are composed. It is often taken to mean the "natural environment" or wilderness–wild animals, rocks, forest, beaches, and in general those things that have not been substantially altered by human intervention, or which persist despite human intervention. For, example, manufactured objects and human interaction generally are not considered part of nature, unless qualified as, for example, "human nature" or "the whole of nature". This more traditional concept of natural things which can still be found today implies a distinction between the natural and the artificial, with the artificial being understood as that which has been brought into being by a human consciousness or a human mind. Depending on the particular context, the term "natural" might also be distinguished from the unnatural, the supernatural, and the artifactual.
Earth
Earth (or, "the earth") is the only planet presently known to support life, and its natural features are the subject of many fields of scientific research. Within the solar system, it is third nearest to the sun; it is the largest terrestrial planet and the fifth largest overall. Its most prominent climatic features are its two large polar regions, two relatively narrow temperate zones, and a wide equatorial tropical to subtropical region.[6] Precipitation varies widely with location, from several metres of water per year to less than a millimetre. 71 percent of the Earth's surface is covered by salt-water oceans. The remainder consists of continents and islands, with most of the inhabited land in the Northern Hemisphere.
Earth has evolved through geological and biological processes that have left traces of the original conditions. The outer surface is divided into several gradually migrating tectonic plates, which have changed relatively quickly several times. [citation needed] The interior remains active, with a thick layer of molten mantle and an iron-filled core that generates a magnetic field.
The atmospheric conditions have been significantly altered from the original conditions by the presence of life-forms,[7] which create an ecological balance that stabilizes the surface conditions. Despite the wide regional variations in climate by latitude and other geographic factors, the long-term average global climate is quite stable during interglacial periods,[8] and variations of a degree or two of average global temperature have historically had major effects on the ecological balance, and on the actual geography of the Earth.[9][10]
Geology
Geology is the science and study of the solid and liquid matter that constitutes the Earth. The field of geology encompasses the study of the composition, structure, physical properties, dynamics, and history of Earth materials, and the processes by which they are formed, moved, and changed. The field is a major academic discipline, and is also important for mineral and hydrocarbon extraction, knowledge about and mitigation of natural hazards, some engineering fields, and understanding past climates and environments.
Geological evolution
The geology of an area evolves through time as rock units are deposited and inserted and deformational processes change their shapes and locations.
Rock units are first emplaced either by deposition onto the surface or intrude into the overlying rock. Deposition can occur when sediments settle onto the surface of the Earth and later lithify into sedimentary rock, or when as volcanic material such as volcanic ash or lava flows, blanket the surface. Igneous intrusions such as batholiths, laccoliths, dikes, and sills, push upwards into the overlying rock, and crystallize as they intrude.
After the initial sequence of rocks has been deposited, the rock units can be deformed and/or metamorphosed. Deformation typically occurs as a result of horizontal shortening, horizontal extension, or side-to-side (strike-slip) motion. These structural regimes broadly relate to convergent boundaries, divergent boundaries, and transform boundaries, respectively, between tectonic plates.
Historical perspective
Earth is estimated to have formed 4.54 billion years ago from the solar nebula, along with the Sun and other planets.[12] The moon formed roughly 20 million years later. Initially molten, the outer layer of the planet cooled, resulting in the solid crust. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, most or all of which came from ice delivered by comets, produced the oceans and other water sources.[13] The highly energetic chemistry is believed to have produced a self-replicating molecule around 4 billion years ago.[14]
Continents formed, then broke up and reformed as the surface of Earth reshaped over hundreds of millions of years, occasionally combining to make a supercontinent. Roughly 750 million years ago, the earliest known supercontinent Rodinia, began to break apart. The continents later recombined to form Pannotia which broke apart about 540 million years ago, then finally Pangaea, which broke apart about 180 million years ago.[15]
There is significant evidence that a severe glacial action during the Neoproterozoic era covered much of the planet in a sheet of ice. This hypothesis has been termed the "Snowball Earth", and it is of particular interest as it precedes the Cambrian explosion in which multicellular life forms began to proliferate about 530–540 million years ago.[16]
Since the Cambrian explosion there have been five distinctly identifiable mass extinctions.[17] The last mass extinction occurred some 65 million years ago, when a meteorite collision probably triggered the extinction of the non-avian dinosaurs and other large reptiles, but spared small animals such as mammals, which then resembled shrews. Over the past 65 million years, mammalian life diversified.[18]
Several million years ago, a species of small African ape gained the ability to stand upright.[19] The subsequent advent of human life, and the development of agriculture and further civilization allowed humans to affect the Earth more rapidly than any previous life form, affecting both the nature and quantity of other organisms as well as global climate. By comparison, the oxygen catastrophe, produced by the proliferation of algae during the Siderian period, required about 300 million years to culminate.
The present era is classified as part of a mass extinction event, the Holocene extinction event, the fastest ever to have occurred.[20][21] Some, such as E. O. Wilson of Harvard University, predict that human destruction of the biosphere could cause the extinction of one-half of all species in the next 100 years.[22] The extent of the current extinction event is still being researched, debated and calculated by biologists.[23]
- REDIRECT Template:Break
Atmosphere, climate, and weather
The atmosphere of the Earth serves as a key factor in sustaining the planetary ecosystem. The thin layer of gases that envelops the Earth is held in place by the planet's gravity. Dry air consists of 78% nitrogen, 21% oxygen, 1% argon and other inert gases, carbon dioxide, etc.; but air also contains a variable amount of water vapor. The atmospheric pressure declines steadily with altitude, and has a scale height of about 8 kilometres at the Earth's surface: the height at which the atmospheric pressure has declined by a factor of e (a mathematical constant equal to 2.71...).[24][25] The ozone layer of the Earth's atmosphere plays an important role in depleting the amount of ultraviolet (UV) radiation that reaches the surface. As DNA is readily damaged by UV light, this serves to protect life at the surface. The atmosphere also retains heat during the night, thereby reducing the daily temperature extremes.
Terrestrial weather occurs almost exclusively in the lower part of the atmosphere, and serves as a convective system for redistributing heat. Ocean currents are another important factor in determining climate, particularly the major underwater thermohaline circulation which distributes heat energy from the equatorial oceans to the polar regions. These currents help to moderate the differences in temperature between winter and summer in the temperate zones. Also, without the redistributions of heat energy by the ocean currents and atmosphere, the tropics would be much hotter, and the polar regions much colder.
Weather can have both beneficial and harmful effects. Extremes in weather, such as tornadoes or hurricanes and cyclones, can expend large amounts of energy along their paths, and produce devastation. Surface vegetation has evolved a dependence on the seasonal variation of the weather, and sudden changes lasting only a few years can have a dramatic effect, both on the vegetation and on the animals which depend on its growth for their food.
The planetary climate is a measure of the long-term trends in the weather. Various factors are known to influence the climate, including ocean currents, surface albedo, greenhouse gases, variations in the solar luminosity, and changes to the planet's orbit. Based on historical records, the Earth is known to have undergone drastic climate changes in the past, including ice ages.
The climate of a region depends on a number of factors, especially latitude. A latitudinal band of the surface with similar climatic attributes forms a climate region. There are a number of such regions, ranging from the tropical climate at the equator to the polar climate in the northern and southern extremes. Weather is also influenced by the seasons, which result from the Earth's axis being tilted relative to its orbital plane. Thus, at any given time during the summer or winter, one part of the planet is more directly exposed to the rays of the sun. This exposure alternates as the Earth revolves in its orbit. At any given time, regardless of season, the northern and southern hemispheres experience opposite seasons.
Weather is a chaotic system that is readily modified by small changes to the environment, so accurate weather forecasting is currently limited to only a few days.[citation needed] Overall, two things are currently happening worldwide: (1) temperature is increasing on the average; and (2) regional climates have been undergoing noticeable changes.[26]
Water on Earth
Water is a chemical substance that is composed of hydrogen and oxygen and is vital for all known forms of life.[27] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71% of the Earth's surface.[28] On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation.[29] Oceans hold 97% of surface water, glaciers and polar ice caps 2.4%, and other land surface water such as rivers, lakes and ponds 0.6%. Additionally, a minute amount of the Earth's water is contained within biological bodies and manufactured products.
Oceans
Earth's oceans |
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An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface (an area of some 361 million square kilometers) is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas. More than half of this area is over 3,000 meters (9,800 ft) deep. Average oceanic salinity is around 35 parts per thousand (ppt) (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ppt. Though generally recognized as several 'separate' oceans, these waters comprise one global, interconnected body of salt water often referred to as the World Ocean or global ocean.[30][31] This concept of a global ocean as a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography.[32]
The major oceanic divisions are defined in part by the continents, various archipelagos, and other criteria: these divisions are (in descending order of size) the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean and the Arctic Ocean. Smaller regions of the oceans are called seas, gulfs, bays and other names. There are also salt lakes, which are smaller bodies of landlocked saltwater that are not interconnected with the World Ocean. Two notable examples of salt lakes are the Aral Sea and the Great Salt Lake.
Lakes
A lake (from Latin lacus) is a terrain feature (or physical feature), a body of liquid on the surface of a world that is localized to the bottom of basin (another type of landform or terrain feature; that is, it is not global) and moves slowly if it moves at all. On Earth, a body of water is considered a lake when it is inland, not part of the ocean, is larger and deeper than a pond, and is fed by a river.[33][34] The only world other than Earth known to harbor lakes is Titan, Saturn's largest moon, which has lakes of ethane, most likely mixed with methane. It is not known if Titan's lakes are fed by rivers, though Titan's surface is carved by numerous river beds. Natural lakes on Earth are generally found in mountainous areas, rift zones, and areas with ongoing or recent glaciation. Other lakes are found in endorheic basins or along the courses of mature rivers. In some parts of the world, there are many lakes because of chaotic drainage patterns left over from the last Ice Age. All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them.
Ponds
A pond is a body of standing water, either natural or man-made, that is usually smaller than a lake. A wide variety of man-made bodies of water are classified as ponds, including water gardens designed for aesthetic ornamentation, fish ponds designed for commercial fish breeding, and solar ponds designed to store thermal energy. Ponds and lakes are distinguished from streams via current speed. While currents in streams are easily observed, ponds and lakes possess thermally driven microcurrents and moderate wind driven currents. These features distinguish a pond from many other aquatic terrain features, such as stream pools and tide pools.
Rivers
A river is a natural watercourse,[35] usually freshwater, flowing toward an ocean, a lake, a sea or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including stream, creek, brook, rivulet, and rill; there is no general rule that defines what can be called a river. Many names for small rivers are specific to geographic location; one example is Burn in Scotland and North-east England. Sometimes a river is said to be larger than a creek,[36] but this is not always the case, due to vagueness in the language.[37] A river is part of the hydrological cycle. Water within a river is generally collected from precipitation through surface runoff, groundwater recharge, springs, and the release of stored water in natural ice and snowpacks (i.e., from glaciers).
Streams
A stream is a flowing body of water with a current, confined within a bed and stream banks. In the United States a stream is classified as a watercourse less than 60 feet (18 metres) wide. Streams are important as conduits in the water cycle, instruments in groundwater recharge, and they serve as corridors for fish and wildlife migration. The biological habitat in the immediate vicinity of a stream is called a riparian zone. Given the status of the ongoing Holocene extinction, streams play an important corridor role in connecting fragmented habitats and thus in conserving biodiversity. The study of streams and waterways in general is known as surface hydrology and is a core element of environmental geography.[38]
Ecosystems
Ecosystems are composed of a variety of abiotic and biotic components that function in an interrelated way.[40] The structure and composition is determined by various environmental factors that are interrelated. Variations of these factors will initiate dynamic modifications to the ecosystem. Some of the more important components are: soil, atmosphere, radiation from the sun, water, and living organisms.
Central to the ecosystem concept is the idea that living organisms interact with every other element in their local environment. Eugene Odum, a founder of ecology, stated: "Any unit that includes all of the organisms (ie: the "community") in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e.: exchange of materials between living and nonliving parts) within the system is an ecosystem."[41] Within the ecosystem, species are connected and dependent upon one another in the food chain, and exchange energy and matter between themselves as well as with their environment.[42] The human ecosystem concept is grounded in the deconstruction of the human/nature dichotomy and the premise that all species are ecologically integrated with each other, as well as with the abiotic constituents of their biotope.[citation needed]
A smaller unit of size is called a microecosystem. For example, a microsystem can be a stone and all the life under it. A macroecosystem might involve a whole ecoregion, with its drainage basin.[43]
Wilderness
Wilderness is generally defined as areas that have not been significantly modified by human activity. The WILD Foundation goes into more detail, defining wilderness as: "The most intact, undisturbed wild natural areas left on our planet - those last truly wild places that humans do not control and have not developed with roads, pipelines or other industrial infrastructure." Wilderness areas can be found in preserves, estates, farms, conservation preserves, ranches, National Forests, National Parks and even in urban areas along rivers, gulches or otherwise undeveloped areas. Wilderness areas and protected parks are considered important for the survival of certain species, ecological studies, conservation, solitude, and recreation. Some nature writers believe wilderness areas are vital for the human spirit and creativity,[44] and some Ecologists consider wilderness areas to be an integral part of the planet's self-sustaining natural ecosystem (the biosphere). They may also preserve historic genetic traits and that they provide habitat for wild flora and fauna that may be difficult to recreate in zoos, arboretums or laboratories.
Life
Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by organization, metabolism, growth, adaptation, response to stimuli and reproduction.[45] Life may also be said to be simply the characteristic state of organisms.
Properties common to terrestrial organisms (plants, animals, fungi, protists, archaea and bacteria) are that they are cellular, carbon-and-water-based with complex organization, having a metabolism, a capacity to grow, respond to stimuli, and reproduce. An entity with these properties is generally considered life. However, not every definition of life considers all of these properties to be essential. Human-made analogs of life may also be considered to be life.
The biosphere is the part of Earth's outer shell – including land, surface rocks, water, air and the atmosphere – within which life occurs, and which biotic processes in turn alter or transform. From the broadest geophysiological point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere (rocks), hydrosphere (water), and atmosphere (air). Currently the entire Earth contains over 75 billion tons (150 trillion pounds or about 6.8 x 1013 kilograms) of biomass (life), which lives within various environments within the biosphere.[46]
Over nine-tenths of the total biomass on Earth is plant life, on which animal life depends very heavily for its existence.[47] More than 2 million species of plant and animal life have been identified to date,[48] and estimates of the actual number of existing species range from several million to well over 50 million.[49][50][51] The number of individual species of life is constantly in some degree of flux, with new species appearing and others ceasing to exist on a continual basis.[52][53] The total number of species is presently in rapid decline.[54][55][56]
Evolution
Life is only known to exist on the planet Earth.(cf Astrobiology) The origin of life is still a poorly understood process, but it is thought to have occurred about 3.9 to 3.5 billion years ago during the hadean or archean eons on a primordial earth that had a substantially different environment than is found at present.[59] These life forms possessed the basic traits of self-replication and inheritable traits. Once life had appeared, the process of evolution by natural selection resulted in the development of ever-more diverse life forms.
Species that were unable to adapt to the changing environment and competition from other life forms became extinct. However, the fossil record retains evidence of many of these older species. Current fossil and DNA evidence shows that all existing species can trace a continual ancestry back to the first primitive life forms.[59]
The advent of photosynthesis in very basic forms of plant life worldwide allowed the sun's energy to be harvested to create conditions allowing for more complex life.[citation needed] The resultant oxygen accumulated in the atmosphere and gave rise to the ozone layer. The incorporation of smaller cells within larger ones resulted in the development of yet more complex cells called eukaryotes.[60] Cells within colonies became increasingly specialized, resulting in true multicellular organisms. With the ozone layer absorbing harmful ultraviolet radiation, life colonized the surface of Earth.
Microbes
The first form of life to develop on the Earth were microbes, and they remained the only form of life on the planet until about a billion years ago when multi-cellular organisms began to appear.[61] Microorganisms are single-celled organisms that are generally microscopic, and smaller than the human eye can see. They include Bacteria, Fungi, Archaea and Protista.
These life forms are found in almost every location on the Earth where there is liquid water, including the interior of rocks within the planet.[62] Their reproduction is both rapid and profuse. The combination of a high mutation rate and a horizontal gene transfer[63] ability makes them highly adaptable, and able to survive in new environments, including outer space.[64] They form an essential part of the planetary ecosystem. However some microorganisms are pathogenic and can post health risk to other organisms.
Plants and animals
Originally Aristotle divided all living things between plants, which generally do not move fast enough for humans to notice, and animals. In Linnaeus' system, these became the kingdoms Vegetabilia (later Plantae) and Animalia. Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the fungi and several groups of algae were removed to new kingdoms. However, these are still often considered plants in many contexts. Bacterial life is sometimes included in flora,[65][66] and some classifications use the term bacterial flora separately from plant flora.
Among the many ways of classifying plants are by regional floras, which, depending on the purpose of study, can also include fossil flora, remnants of plant life from a previous era. People in many regions and countries take great pride in their individual arrays of characteristic flora, which can vary widely across the globe due to differences in climate and terrain.
Regional floras commonly are divided into categories such as native flora and agricultural and garden flora, the lastly mentioned of which are intentionally grown and cultivated. Some types of "native flora" actually have been introduced centuries ago by people migrating from one region or continent to another, and become an integral part of the native, or natural flora of the place to which they were introduced. This is an example of how human interaction with nature can blur the boundary of what is considered nature.
Another category of plant has historically been carved out for weeds. Though the term has fallen into disfavor among botanists as a formal way to categorize "useless" plants, the informal use of the word "weeds" to describe those plants that are deemed worthy of elimination is illustrative of the general tendency of people and societies to seek to alter or shape the course of nature. Similarly, animals are often categorized in ways such as domestic, farm animals, wild animals, pests, etc. according to their relationship to human life.
Animals as a category have several characteristics that generally set them apart from other living things, though this is not traced by scientists to having legs or wings instead of roots and leaves.[citation needed] Animals are eukaryotic and usually multicellular (although see Myxozoa), which separates them from bacteria, archaea and most protists. They are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls.
With a few exceptions, most notably the sponges (Phylum Porifera), animals have bodies differentiated into separate tissues.[citation needed] These include muscles, which are able to contract and control locomotion, and a nervous system, which sends and processes signals. There is also typically an internal digestive chamber. The eukaryotic cells possessed by all animals are surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. This may be calcified to form structures like shells, bones, and spicules, a framework upon which cells can move about and be reorganized during development and maturation, and which supports the complex anatomy required for mobility.
Human interrelationship
Although humans currently comprise only a minuscule proportion of the total living biomass on Earth, the human effect on nature is disproportionately large. Because of the extent of human influence, the boundaries between what humans regard as nature and "made environments" is not clear cut except at the extremes. Even at the extremes, the amount of natural environment that is free of discernible human influence is presently diminishing at an increasingly rapid pace.
The development of technology by the human race has allowed the greater exploitation of natural resources and has helped to alleviate some of the risk from natural hazards. In spite of this progress, however, the fate of human civilization remains closely linked to changes in the environment. There exists a highly complex feedback loop between the use of advanced technology and changes to the environment that are only slowly becoming understood.[67] Man-made threats to the Earth's natural environment include pollution, deforestation, and disasters such as oil spills. Humans have contributed to the extinction of many plants and animals.
Humans employ nature for both leisure and economic activities. The acquisition of natural resources for industrial use remains the primary component of the world's economic system. [citation needed] Some activities, such as hunting and fishing, are used for both sustenance and leisure, often by different people. Agriculture was first adopted around the 9th millennium B.C.E. Ranging from food production to energy, nature influences economic wealth.
Although early humans gathered uncultivated plant materials for food and employed the medicinal properties of vegetation for healing,[68] most modern human use of plants is through agriculture. The clearance of large tracts of land for crop growth has led to a significant reduction in the amount available of forestation and wetlands, resulting in the loss of habitat for many plant and animal species as well as increased erosion.[69]
Aesthetics and beauty
Beauty in nature has historically been a prevalent theme in art and books, filling large sections of libraries and bookstores. That nature has been depicted and celebrated by so much art, photography, poetry and other literature shows the strength with which many people associate nature and beauty. Reasons why this association exists, and what the association consists of, is studied by the branch of philosophy called aesthetics. Beyond certain basic characteristics that many philosophers agree about to explain what is seen as beautiful, the opinions are virtually endless.[70] Nature and wildness have been important subjects in various epochs of world history. An early tradition of landscape art began in China during the Tang Dynasty (618-907). The tradition of representing nature as it is became one of the aims of Chinese painting and was a significant influence in Asian art.
Although natural wonders are celebrated in the Psalms and the Book of Job, wilderness portrayals in art became more prevalent in the 1800s, especially in the works of the Romantic movement. British artists John Constable and JMW Turner turned their attention to capturing the beauty of the natural world in their paintings. Before that, paintings had been primarily of religious scenes or of human beings. William Wordsworth's poetry described the wonder of the natural world, which had formerly been viewed as a threatening place. Increasingly the valuing of nature became an aspect of Western culture.[71] This artistic movement also coincided with the Transcendentalist movement in the Western world. A common classical idea of beautiful art involves the word mimesis, the imitation of nature. Also in the realm of ideas about beauty in nature is that the perfect is implied through symmetry, equal division, and other perfect mathematical forms and notions. [citation needed]
Matter and energy
- See also: Chemistry and Physics
Some fields of science see nature as matter in motion, obeying certain laws of nature which science seeks to understand. For this reason the most fundamental science is generally understood to be "physics" – the name for which is still recognizable as meaning that it is the study of nature.
Matter is commonly defined as the substance of which physical objects are composed. It constitutes the observable universe. The visible components of the universe are now believed to compose only 4 percent of the total mass. The remainder is believed to consist of 23 percent cold dark matter and 73 percent dark energy.[72] The exact nature of these components is still unknown and is currently under intensive investigation by physicists.
The behavior of matter and energy throughout the observable universe appears to follow well-defined physical laws. These laws have been employed to produce cosmological models that successfully explain the structure and the evolution of the universe we can observe. The mathematical expressions of the laws of physics employ a set of twenty physical constants[73] that appear to be static across the observable universe.[74] The values of these constants have been carefully measured, but the reason for their specific values remains a mystery.
Beyond Earth
Outer space, also simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. Outer space is used to distinguish it from airspace (and terrestrial locations). There is no discrete boundary between the Earth's atmosphere and space, as the atmosphere gradually attenuates with increasing altitude. Outer space within the solar system is called interplanetary space, which passes over into interstellar space at what is known as the heliopause.
Outer space is certainly spacious, but it is far from empty. [citation needed] Outer space is sparsely filled with several dozen types of organic molecules discovered to date by microwave spectroscopy, blackbody radiation left over from the big bang and the origin of the universe, and cosmic rays, which include ionized atomic nuclei and various subatomic particles. There is also some gas, plasma and dust, and small meteors. Additionally, there are signs of human life in outer space today, such as material left over from previous manned and unmanned launches which are a potential hazard to spacecraft. Some of this debris re-enters the atmosphere periodically.
Although the planet Earth is currently the only known body within the solar system to support life, current evidence suggests that in the distant past the planet Mars possessed bodies of liquid water on the surface.[75] For a brief period in Mars' history, it may have also been capable of forming life. At present though, most of the water remaining on Mars is frozen. If life exists at all on Mars, it is most likely to be located underground where liquid water can still exist.[76]
Conditions on the other terrestrial planets, Mercury and Venus, appear to be too harsh to support life as we know it. [citation needed] But it has been conjectured that Europa, the fourth-largest moon of Jupiter, may possess a sub-surface ocean of liquid water and could potentially host life.[77]
Recently, the team of Stéphane Udry have discovered a new planet named Gliese 581 g, which is an extrasolar planet orbiting the red dwarf star Gliese 581. [citation needed] Gliese 581 g appears to lie in the habitable zone of space surrounding the star, and therefore could possibly host life as we know it.
See also
Template:Wikipedia-Books Template:Portal box
Science:
- Natural history
- Natural science
- Natural landscape
Philosophy:
- Mother Nature
- Nature (philosophy)
- Naturalism (philosophy): any of several philosophical stances, typically those descended from Materialism and Pragmatism that do not distinguish the supernatural from nature. [citation needed] This includes the methodological naturalism of natural science, which makes the methodological assumption that observable events in nature are explained only by natural causes, without assuming either the existence or non-existence of the supernatural.
- Balance of nature (biological fallacy): A discredited concept of natural equilibrium in predator:prey dynamics.
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Notes and references
- ↑ Harper, Douglas. nature. Online Etymology Dictionary.
- ↑ A useful though somewhat erratically presented account of the pre-Socratic use of the concept of φύσις may be found in Naddaf, Gerard The Greek Concept of Nature, SUNY Press, 2006. The word φύσις, while first used in connection with a plant in Homer, occurs very early in Greek philosophy, and in several senses. Generally, these senses match rather well the current senses in which the English word nature is used, as confirmed by Guthrie, W.K.C. Presocratic Tradition from Parmenides to Democritus (volume 2 of his History of Greek Philosophy), Cambridge UP, 1965.
- ↑ The first known use of physis was by Homer in reference to the intrinsic qualities of a plant: ὣς ἄρα φωνήσας πόρε φάρμακον ἀργεϊφόντης ἐκ γαίης ἐρύσας, καί μοι φύσιν αὐτοῦ ἔδειξε. (So saying, Argeiphontes [=Hermes] gave me the herb, drawing it from the ground, and showed me its nature.) Odyssey 10.302-3 (ed. A.T. Murray). (The word is dealt with thoroughly in Liddell and Scott's Greek Lexicon.) For later but still very early Greek uses of the term, see earlier note.
- ↑ Isaac Newton's Philosophiae Naturalis Principia Mathematica (1687), for example, is translated "Mathematical Principles of Natural Philosophy", and reflects the then-current use of the words "natural philosophy", akin to "systematic study of nature"
- ↑ The etymology of the word "physical" shows its use as a synonym for "natural" in about the mid-15th century: Harper, Douglas. physical. Online Etymology Dictionary.
- ↑ World Climates. Blue Planet Biomes. Retrieved 2006-09-21.
- ↑ Calculations favor reducing atmosphere for early Earth. Science Daily (2005-09-11). Retrieved 2007-01-06.
- ↑ Past Climate Change. U.S. Environmental Protection Agency. Retrieved 2007-01-07.
- ↑ Hugh Anderson, Bernard Walter (March 28, 1997). History of Climate Change. NASA. Archived from the original on 2008-01-23. Retrieved 2007-01-07.
- ↑ Weart, Spencer (June 2006). The Discovery of Global Warming. American Institute of Physics. Retrieved 2007-01-07.
- ↑ Margulis, Lynn and Dorian Sagan (1995). What is Life?. New York: Simon & Schuster. ISBN 0684813262.
- ↑ Dalrymple, G. Brent (1991). The Age of the Earth. Stanford: Stanford University Press. ISBN 0-8047-1569-6.
- ↑ Morbidelli, A. and et al. (2000). Source Regions and Time Scales for the Delivery of Water to Earth. Meteoritics & Planetary Science 35 (6): 1309–1320.
- ↑ "Earth's Oldest Mineral Grains Suggest an Early Start for Life", NASA Astrobilogy Institute, 2001-12-24. Retrieved 2006-05-24.
- ↑ Murphy, J.B. and R.D. Nance (2004). How do supercontinents assemble?. American Scientist 92 (4): 324.
- ↑ Kirschvink, J.L. (1992). "Late Proterozoic Low-Latitude Global Glaciation: The Snowball Earth", in J.W. Schopf, C. Klein eds.: The Proterozoic Biosphere. Cambridge: Cambridge University Press, 51–52. ISBN 0-521-36615-1.
- ↑ Raup, David M. and J. John Sepkoski Jr. (March 1982). Mass extinctions in the marine fossil record. Science 215 (4539): 1501–3.
- ↑ Margulis, Lynn and Dorian Sagan (1995). What is Life?. New York: Simon & Schuster, 145. ISBN 0-684-81326-2.
- ↑ Margulis, Lynn and Dorian Sagan (1995). What is Life?. New York: Simon & Schuster. ISBN 0-684-81326-2.
- ↑ Diamond J (1989). The present, past and future of human-caused extinctions. Philos Trans R Soc Lond B Biol Sci 325 (1228): 469–76; discussion 476–7.
- ↑ Novacek M, Cleland E (2001). The current biodiversity extinction event: scenarios for mitigation and recovery. Proc Natl Acad Sci USA 98 (10): 1029.
- ↑ "The mid-Holocene extinction of silver fir (Abies alba) in the ..." pdf
- ↑ See, e.g. [1], [2], [3]
- ↑ Ideal Gases under Constant Volume, Constant Pressure, Constant Temperature, & Adiabatic Conditions. NASA. Retrieved 2007-01-07.
- ↑ Pelletier, Jon D. (2002). Natural variability of atmospheric temperatures and geomagnetic intensity over a wide range of time scales. Proceedings of the National Academy of Sciences 99: 2546–2553.
- ↑ "Tropical Ocean Warming Drives Recent Northern Hemisphere Climate Change", Science Daily, April 6, 2001. Retrieved 2006-05-24.
- ↑ United Nations
- ↑ CIA- The world fact book. Central Intelligence Agency. Retrieved 2008-12-20.
- ↑ Water Vapor in the Climate System, Special Report, [AGU], December 1995 (linked 4/2007). Vital Water UNEP.
- ↑ "Ocean". The Columbia Encyclopedia. 2002. New York: Columbia University Press
- ↑ "Distribution of land and water on the planet". UN Atlas of the Oceans
- ↑ Spilhaus, Athelstan F. 1942 (Jul.). "Maps of the whole world ocean." Geographical Review (American Geographical Society). Vol. 32 (3): pp. 431-5.
- ↑ Brittanica online. Lake (physical feature). Retrieved 2008-06-25.
- ↑ [http://dictionary.reference.com/browse/lake a body of fresh or salt water of considerable size, surrounded by land. Dictionary.com definition]. Retrieved 2008-06-25.
- ↑ River {definition} from Merriam-Webster. Accessed February 2010.
- ↑ River, Wordnet
- ↑ USGS - U.S. Geological Survey - faqs, #17 What is the difference between mountain, hill, and peak; lake and pond; or river and creek?
- ↑ http://ga.water.usgs.gov/edu/hydrology.html/
- ↑ Adams, C.E. (1994). The fish community of Loch Lomond, Scotland : its history and rapidly changing status. Hydrobiologia 290 (1-3): 91–102.
- ↑ Pidwirny, Michael (2006). Introduction to the Biosphere: Introduction to the Ecosystem Concept. Fundamentals of Physical Geography (2nd Edition). Retrieved September 28, 2006.
- ↑ Odum, EP (1971) Fundamentals of ecology, third edition, Saunders New York
- ↑ Pidwirny, Michael (2006). Introduction to the Biosphere: Organization of Life. Fundamentals of Physical Geography (2nd Edition). Retrieved September 28, 2006.
- ↑ Bailey, Robert G. (April 2004). Identifying Ecoregion Boundaries. Environmental Management 34 (Supplement 1): S14.
- ↑ No Man's Garden by Daniel B. Botkin p155-157
- ↑ Definition of Life. California Academy of Sciences (2006). Retrieved 2007-01-07.
- ↑ The figure "about one-half of one percent" takes into account the following (See, e.g., Leckie, Stephen (1999). "How Meat-centred Eating Patterns Affect Food Security and the Environment", For hunger-proof cities : sustainable urban food systems. Ottawa: International Development Research Centre. ISBN 0-88936-882-1. , which takes global average weight as 60 kg.), the total human biomass is the average weight multiplied by the current human population of approximately 6.5 billion (see, e.g., World Population Information. U.S. Census Bureau. Retrieved September 28, 2006.): Assuming 60–70 kg to be the average human mass (approximately 130–150 lb on the average), an approximation of total global human mass of between 390 billion (390×109) and 455 billion kg (between 845 billion and 975 billion lb, or about 423 million–488 million short tons). The total biomass of all kinds on earth is estimated to be in excess of 6.8 x 1013 kg (75 billion short tons). By these calculations, the portion of total biomass accounted for by humans would be very roughly 0.6%.
- ↑ Sengbusch, Peter V.. The Flow of Energy in Ecosystems - Productivity, Food Chain, and Trophic Level. Botany online. University of Hamburg Department of Biology. Retrieved September 23, 2006.
- ↑ Pidwirny, Michael (2006). Introduction to the Biosphere: Species Diversity and Biodiversity. Fundamentals of Physical Geography (2nd Edition). Retrieved September 23, 2006.
- ↑ How Many Species are There?. Extinction Web Page Class Notes. Retrieved September 23, 2006.
- ↑ "Animal." World Book Encyclopedia. 16 vols. Chicago: World Book, 2003. This source gives an estimate of from 2 to 50 million.
- ↑ Just How Many Species Are There, Anyway?. Science Daily (May 2003). Retrieved September 26, 2006.
- ↑ Withers, Mark A.; et al. (1998). Changing Patterns in the Number of Species in North American Floras. Land Use History of North America. Retrieved September 26, 2006. Website based on the contents of the book: (1998) in Sisk, T.D., ed.: Perspectives on the land use history of North America: a context for understanding our changing environment, Revised September 1999, U.S. Geological Survey, Biological Resources Division. USGS/BRD/BSR-1998-0003.
- ↑ Tropical Scientists Find Fewer Species Than Expected. Science Daily (April 2002). Retrieved September 27, 2006.
- ↑ Bunker, Daniel E. and et al. (November 2005). Species Loss and Aboveground Carbon Storage in a Tropical Forest. Science 310 (5750): 1029–31.
- ↑ Wilcox, Bruce A. (March 2006). Amphibian Decline: More Support for Biocomplexity as a Research Paradigm. EcoHealth 3 (1): 1.
- ↑ (2002) "Decline and loss of species", in Clarke, Robin, Robert Lamb, Dilys Roe Ward eds.: Global environment outlook 3 : past, present and future perspectives. London; Sterling, VA: Nairobi, Kenya : UNEP. ISBN 92-807-2087-2.
- ↑ http://earthobservatory.nasa.gov/Newsroom/view.php?id=28907
- ↑ http://www.sciencedaily.com/releases/2005/12/051205163236.htm
- ↑ 59.0 59.1 Line M (1 January 2002). The enigma of the origin of life and its timing. Microbiology 148 (Pt 1): 21–7.
- ↑ Berkner, L. V. and L. C. Marshall (May 1965). On the Origin and Rise of Oxygen Concentration in the Earth's Atmosphere. Journal of the Atmospheric Sciences 22 (3): 225–261.
- ↑ Schopf J (1994). Disparate rates, differing fates: tempo and mode of evolution changed from the Precambrian to the Phanerozoic.. Proc Natl Acad Sci USA 91 (15): S14.
- ↑ Szewzyk U, Szewzyk R, Stenström T (1994). Thermophilic, anaerobic bacteria isolated from a deep borehole in granite in Sweden.. Proc Natl Acad Sci USA 91 (5): 1810–3.
- ↑ Wolska K (2003). Horizontal DNA transfer between bacteria in the environment.. Acta Microbiol Pol 52 (3): 233–43.
- ↑ Horneck G (1981). Survival of microorganisms in space: a review.. Adv Space Res 1 (14): 39–48.
- ↑ flora. Merriam-Webster Online Dictionary. Merriam-Webster. Retrieved September 27, 2006.
- ↑ (1998) "Glossary", Status and Trends of the Nation's Biological Resources. Reston, VA: Department of the Interior, Geological Survey. SuDocs No. I 19.202:ST 1/V.1-2.
- ↑ "Feedback Loops In Global Climate Change Point To A Very Hot 21st Century", Science Daily, May 22, 2006. Retrieved 2007-01-07.
- ↑ Plant Conservation Alliance - Medicinal Plant Working Groups Green Medicine. US National Park Services. Retrieved September 23, 2006.
- ↑ Oosthoek, Jan (1999). Environmental History: Between Science & Philosophy. Environmental History Resources. Retrieved 2006-12-01.
- ↑ For an example of a range of opinions, see: On the Beauty of Nature. The Wilderness Society. Retrieved September 29, 2006. and Ralph Waldo Emerson's analysis of the subject: Emerson, Ralph Waldo (1849). "Beauty", Nature; Addresses and Lectures.
- ↑ History of Conservation BC Spaces for Nature. Accessed: May 20, 2006.
- ↑ Some Theories Win, Some Lose. WMAP Mission: First Year Results. NASA. Retrieved 29 2006.
- ↑ Taylor, Barry N. (1971). Introduction to the constants for nonexperts. National Institute of Standards and Technology. Retrieved 2007-01-07.
- ↑ D. A. Varshalovich, A. Y. Potekhin, A. V. Ivanchik (2000). Testing cosmological variability of fundamental constants. AIP Conference Proceedings 506: 503.
- ↑ Bibring, J and Langevin Y, Mustard J, Poulet F, Arvidson R, Gendrin A, Gondet B, Mangold N, Pinet P, Forget F, Berthé M, Bibring J, Gendrin A, Gomez C, Gondet B, Jouglet D, Poulet F, Soufflot A, Vincendon M, Combes M, Drossart P, Encrenaz T, Fouchet T, Merchiorri R, Belluci G, Altieri F, Formisano V, Capaccioni F, Cerroni P, Coradini A, Fonti S, Korablev O, Kottsov V, Ignatiev N, Moroz V, Titov D, Zasova L, Loiseau D, Mangold N, Pinet P, Douté S, Schmitt B, Sotin C, Hauber E, Hoffmann H, Jaumann R, Keller U, Arvidson R, Mustard J, Duxbury T, Forget F, Neukum G (2006). Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data. Science 312 (5772): 400–4.
- ↑ Malik, Tariq (2005-03-08). Hunt for Mars life should go underground. The Brown University News Bureau. Retrieved September 4, 2006.
- ↑ Scott Turner (1998-03-02). Detailed Images From Europa Point To Slush Below Surface. The Brown University News Bureau. Retrieved September 28, 2006.
External links
- Nature Journal - Weekly journal of science.
- The WILD Foundation.
- BBC - Science and Nature.
- European Commission - Nature and Biodiversity homepage.
- The Nature Conservancy
- Science.gov - Environment & Environmental Quality.
- wallpapers nature.
- NatureWatch - Wiki for documenting biodiversity (german)
- Ministry of Environment Republic of Korea - Nature
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